Ascii value of a to z Java program

Posted by: Instanceofjava Posted date: February 02, 2025 / comment : 0

 Understanding ASCII and How to Print ASCII Values in Java

ASCII is a character encoding standard: It is used to represent text in computers and other devices. Each of its characters is assigned a unique numerical value comprising, amongst others, letters, digits, punctuation and control. For example, the ASCII value of the letter 'A' is 65, and of the letter 'a' is 97.

In this blog post I will explain a simple Java program that outputs the ASCII values for lower case letters deathnbsp;'a' to 'z'; this helps you understand how characters are actually represented by the computer as well as work with ASCII values in Java.

What is ASCII

ASCII is a 7-bit character encoding standard that can represent 128 characters (0 to 127). These characters include:

Uppercase letters: A to Z (ASCII values 65 to 90)

Lowercase letters: a to z (ASCII values 97 to 122)

Digits: 0 to 9 (ASCII values 48 to 57)

Special characters: !, @, #, $, etc.

Control characters: Newline (\n), tab (\t), etc.

Subsequently, when writing programs for programming matrix (i.e. application software), you will want to use ASCII values instead of characters themselves in order to handle different character sets: for example to sort escort compare different characters.

Java program to print ASCII values from a to z

public class AsciiValues {

    public static void main(String[] args) {

        // Loop through characters 'a' to 'z'

        for (char ch = 'a'; ch <= 'z'; ch++) {

            // Print the character and its ASCII value

            System.out.println("Character: " + ch + ", ASCII Value: " + (int) ch);

        }

    }

}

semicolon in java

Posted by: Instanceofjava Posted date: January 21, 2023 / comment : 0

 a semicolon (;) is used to separate statements in a program. Each statement in a Java program must end with a semicolon, just like in many other programming languages.

Here's an example of  semicolon in a Java program:

int x = 5; // Declare a variable and assign a value

System.out.println(x); // Print the value of the variable

x++; // Increment the value of the variable

System.out.println(x); // Print the new value of the variable

In this example, there are three statements: one for declaring a variable and assigning a value, one for printing the value of the variable, and one for incrementing the value of the variable. Each statement ends with a semicolon, which separates them from each other.

It's worth noting that, in Java, a semicolon is not always necessary. For example, if you are defining a class or method, you don't need to use a semicolon at the end of the definition. Also, you don't need to use a semicolon after a block statement (statements enclosed in curly braces {}) that is part of a control statement such as if-else, while, for, etc. The end of the block statement is represented by the closing curly brace.

In the case of a single-line if statement or a single-line loop, you can also omit the curly braces {} and write the statement directly after the if or while keyword, respectively.

if(x==5) System.out.println("x is 5");

while(x<10) x++;

In summary, a semicolon is used in Java to separate statements and mark the end of a statement. However, it's not always required and depends on the context of the statement or block.

It's worth noting that in Java, a semicolon is also used in certain control statements such as the "for" loop and the "enhanced for" (or "for-each") loop.

In a "for" loop, the initialization, condition, and increment/decrement statements are separated by semicolons. 


In this example, the initialization statement "int i = 0" is executed once before the loop starts, the condition "i < 10" is checked before each iteration, and the increment statement "i++" is executed after each iteration. Each of these statements is separated by a semicolon.

In the case of the "enhanced for" loop, the semicolon is used to separate the loop variable and the array or collection that is being iterated over.

Instance variables in java with example program

Posted by: Instanceofjava Posted date: January 30, 2018 / comment : 0

  • Variables declared inside a class and outside method without static keyword known as instance variables.
  • Instance variables will be used by objects to store state of the object.
  • Every object will have their own copy of instance variables. where as static variables will be single and shared(accessed) among objects.
  • Instance variables will be associated with the instance(Object)
  • Static variables will be associated with the class.



#1: Java example program on declaring and accessing instance variables.

  1. package com.instanceofjava.instancevariables;

  3. /**
  4.  * @author www.Instanceofjava.com
  5.  * @category interview questions
  6.  * 
  7.  * Description: Instance variables in java with example program
  8.  *
  9.  */
  10. public class InstanceVariables {

  12. String websiteName;
  13. String category;
  15. public static void main(String[] args) {
  17. InstanceVariables obj = new InstanceVariables();
  18. obj.websiteName="www.InstanceOfJava.com";
  19. obj.category="Java tutorial/interview questions";

  22. }

  24. }


  • Instance variables allows all four type of access specifiers in java


instance variables in java with example



  • Instance variables can be final and transient


instance variables in java with example program



  • Instance variables can not be declared as abstract, static strictfp, synchronized and native

Java read file line by line example program

Posted by: Instanceofjava Posted date: January 29, 2018 / comment : 0 ,

  • Reading a text file line by line in java can be done by using java.io.BufferedReader .
  • Create a BufferedReader class by passing new FileReader(new File("filename")) object to it's constructor.
  • By using readLine() method of  BufferedReader class we can read line by line text from a text file as Strings.
  • Lets see a java example program on hoe to read data from file line by line using BufferedReader class readLine() method.
  • Java read lines from text file example program.


#1: Java Example program to read file line by line

 

  1. package com.instanceofjava.readfile;
  2.  
  3. import java.io.BufferedReader;
  4. import java.io.File;
  5. import java.io.FileReader;
  6. import java.io.IOException;
  7. /** *  * 
  8. @author www.instanceofjava.com 
  9. * @category: Interview Programs 
  10. * @description: How to read text file line by line in java example program 
  11. * */
  12.  
  13. public class ReadFile {
  14.  
  15.     public static void main(String[] args) {        
  16.         
  17.         try {            
  18.            File fileName = new File("E:\\data.txt");
  19.             FileReader fileReader = new FileReader(fileName);     
  20.             BufferedReader bufferedreader = new BufferedReader(fileReader);           
  21.             StringBuffer sb = new StringBuffer();
  22.             String strLine;            
  23.            while ((strLine = bufferedreader.readLine()) != null) {
  24.                 sb.append(strLine);
  25.                 sb.append("\n");        
  26.             }         
  27.            fileReader.close();
  28.            System.out.println(sb.toString()); 
  29.          } catch (IOException e) {
  30.             e.printStackTrace();     
  31.    }
  32.  
  33.     }
  34.  
  35. }

Output:

  1. java read file line by line example
  2. java read file line by line java 8
  3. java read lines from text file 
  4. example bufferedreader java example

#2: Java example program to read text file line by line using java 7 try with resource example



read file line by line java


#3: Java example program to read text file line by line using java 8 example (Using stream)

  1. package com.instanceofjava.readfile;
  2. import java.io.IOException;
  3. import java.nio.file.Files;
  4. import java.nio.file.Paths;
  5. import java.util.stream.Stream;
  6. /**
  7.  *
  8. * @author www.instanceofjava.com
  9.  * @category: Interview Programs 
  10. * @description: How to read text file line by line in java example program using java 8 stream
  11. * 
  12. */
  13. public class ReadFile {
  14. public static void main(String[] args) throws IOException {
  15.  
  16. try (Stream<String> stream = Files.lines(Paths.get("E:\\data.txt"))) 
  17. {           
  18.  
  19.  stream.forEach(System.out::println);
  20.  
  21. }
  22. }
  23. }

Convert to maven project in eclipse java

Posted by: Instanceofjava Posted date: January 26, 2018 / comment : 0 ,

  • In order to convert any java project in to maven using eclipse we need to install m2e plugin.
  • Latest versions of eclipse are coming with this m2e plugin by default.
  • If not found this plugin we can install it by help->install->click on add and enter http://download.eclipse.org/technology/m2e/releases. 
  • currently i am using eclipse oxygen version so it is having m2e plugin.
  • I have created a normal java project and i want to convert that into a maven project.
  • To convert any project in to maven right click on the project and ->configure->convert to maven project. 
  • After that a window will be opened and you need to enter group id and artifact id and then click on finish.  
  • convert to maven project eclipse luna / convert to maven project is not visible in eclipse /convert to maven project option not available in eclipse.



Right click on project and select configure-> convert to maven project.


convert to maven project java

Project will be converted to maven by creating pom.xml file.

how to convert to maven project java

 

pom.xml

  1. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.or
  2. /2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
  3. http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.   <modelVersion>4.0.0</modelVersion>
  5.   <groupId>com.instanceofjava.maven</groupId>
  6.   <artifactId>MavenProject</artifactId>
  7.   <version>0.0.1-SNAPSHOT</version>
  8.   <build>
  9.     <sourceDirectory>src</sourceDirectory>
  10.     <plugins>
  11.       <plugin>
  12.         <artifactId>maven-compiler-plugin</artifactId>
  13.         <version>3.7.0</version>
  14.         <configuration>
  15.           <source>1.8</source>
  16.           <target>1.8</target>
  17.         </configuration>
  18.       </plugin>
  19.     </plugins>
  20.   </build>
  21. </project>

Add dependencies to your pom.xml file

  1.  <properties>
  2.         <springVersion>5.0.3.RELEASE</springVersion>
  3.       </properties>
  4.       <dependencies>
  5.         <dependency>
  6.           <groupId>org.springframework</groupId>
  7.           <artifactId>spring-context</artifactId>
  8.           <version>${springVersion}</version>
  9.         </dependency>
  10.        <dependency>
  11.          <groupId>org.springframework</groupId>
  12.          <artifactId>spring-core</artifactId>
  13.           <version>5.0.3.RELEASE</version>
  14.         </dependency>
  15.       </dependencies>

Java finally block after return statement

Posted by: Instanceofjava Posted date: November 15, 2017 / comment : 0

  • finally block will be executed always even exception occurs.
  • If we explicitly call System.exit() method then only finally block will not be executed if exit() call is before finally block.
  • There are few more rare scenarios where finally block will not be executed.
  1. When JVM crashes
  2. When there is an infinite loop
  3. When we kill the process ex:kill -9 (on unix)
  4. Power failure, hardware error or system crash.
  5. And as we discussed System.exit().
  •  Other than these conditions finally block will be executed always.
  • finally block is meant to keep cleaning of resources. Placing code other than cleaning is a bad practice
  • What happens if we place finally block after return statement? or
  • Does finally block will execute after return statement??
  •  As per the above rules Yes finally will always execute except any interruption like System.exit()  or all above mentioned conditions

 Program #1 : Java example program which explains how finally block will be executed even after a return statement in a method.

  1. package com.instanceofjava.finallyblockreturn;
  2. /**
  3.  * By: www.instanceofjava.com
  4.  * program: does finally gets executed after return statement??
  5.  *
  6.  */
  7. public class FinallyBlockAfterReturn {
  8.  
  9.     public static int Calc(){
  10.         try {
  11.             
  12.             return 0;
  13.         } catch (Exception e) {
  14.             return 1;
  15.         }
  16.  
  17. finally{
  18.             
  19.  System.out.println("finally block will be executed even when we
  20. place after return statement");
  21.         }
  22.  }
  23.     
  24. public static void main(String[] args) {
  25.         
  26.         System.out.println(Calc());         
  27. }
  28.  
  29. }



  
Output:


  1. finally block will be executed even when we place after return statement
  2. 0


 Can we place return statement in finally??
  • Yes we can place return statement in finally and finally block return statement will be executed.
  • But it is a very bad practice to place return statement in finally block.
Program #2 : Java example program which explains finally block with return statement in a method.



finally block after return statement

Advantages and disadvantages of arrays in java

Posted by: Instanceofjava Posted date: May 07, 2017 / comment : 2 ,


Disadvantages of array in java
  • Arrays are Strongly Typed.
  • Arrays does not have add or remove methods.
  • We need to mention the size of the array. Fixed length.
  • So there is a chance of memory wastage.
  • To delete an element in an array we need to traverse through out the array so this will reduce performance.
  • Arrays have a fixed size, which means that their size cannot be changed once they are created. This can be a disadvantage when working with dynamic data sets that need to grow or shrink in size.
  • Arrays are not suitable for storing large numbers of different types of elements, it is best used when the data is of a single type.
  • Insertion and deletion operations on arrays can be slow, as they require shifting elements to make room for new elements or close the gap left by deleted elements.
  • Accessing an element in an array can be slow if the array is large, and the index of the element is not known in advance.



Advantages of arrays:


  • We can access any element randomly by using indexes provided by arrays.
  • Primitive type to wrapper classes object conversion will not happen so it is fast.
  • Array can store many number of elements at a time.
  • Arrays have a fixed size, which means that their size cannot be changed once they are created. This can make it easier to manage memory usage and avoid runtime errors caused by dynamic memory allocation.
  • Arrays are relatively fast and efficient. They have a constant time complexity for basic operations such as accessing and updating elements, which makes them suitable for large data sets.
  • Arrays are easy to understand and use, and they are supported by many built-in methods in the Java API, such as Arrays.sort(), Arrays.binarySearch(), and Arrays.toString().



Arrays in java InstanceOfJava

Java interview programs on arrays:

  • Check below for some of the interesting java interview programs on arrays.

Five different ways to print arrays in java:



Creating array of objects in java:



Java program to find missing numbers in an array:



Find second highest number in java arrays:




Convert arrayList to array:

Copy all elements of  hash set to Object array:


Java xor operator with example programs

Posted by: Instanceofjava Posted date: May 06, 2017 / comment : 0


Java Bitwise XOR operator:

In Java, you can use the ^ operator to perform a bitwise exclusive or (XOR) operation on two integers. The XOR operation compares each bit of the first number to the corresponding bit of the second number. If the bits are the same, the corresponding result bit is set to 0.  
The matching result bit is set to 1 if the bits vary.
Here's an example:

int a = 12; // binary: 1100
int b = 25; // binary: 11001
int result = a ^ b;
System.out.println("Result of XOR operation: " + result);

In this example, the XOR operation compares the bits of the integers a and b. Since the bits at positions 2 and 3 are different, the corresponding result bits are set to 1. Therefore the binary representation of result is 01101 which decimal representation is 13
This will output:

Result of XOR operation: 13

It's important to note that XOR operation is not only limited to integers. You can also perform it on bytes or even on bytes of an array, by applying the operation on each element of array.


byte[] array1 = {0, 1, 2, 3, 4, 5};
byte[] array2 = {5, 4, 3, 2, 1, 0};
byte[] result = new byte[6];

for (int i = 0; i < 6; i++) {
    result[i] = (byte) (array1[i] ^ array2[i]);
}

It's also useful for some cryptographic algorithms for example the One Time Pad encryption, where the XOR operation is used to encrypt and decrypt the data.
  • Java bit wise Xor operator operates on bits of numbers.
  • It will be represented as "^".
  • XOR will return true if  both bits are different.
  •  For example 1 XOR 0 gives 1. Ex: 1^0=1.
  • 0^1=1.




 Java Bitwise Xor:

Java bitwise XOR operator


Program#1:Java Example program on two integer numbers Xor operation.


  1. package com.Xorinjava;
  2. public class XOR {
  3.     /**
  4.     * Xor in java Xor example program
  5.     * @author www.instanceofjava.com
  6.     */
  7.     public static void main(String[] args) {
  8.         int a=1;
  9.         int b=0;
  10.         int c= a^b;
  11.         
  12.         System.out.println(c);
  13.  
  14.     }
  15.  
  16. }
Output:

  1. 1

Program #2: java xor boolean expression : java example program


  1. package com.Xorinjava;
  2.  
  3. public class XOR {
  4.     /**
  5.     * Xor in java boolean Xor example program
  6.     * @author www.instanceofjava.com
  7.     */
  8. public static void main(String[] args) {
  9.         boolean a=true;
  10.         boolean b=false;
  11.         boolean c= a^b;
  12.         
  13.         System.out.println(c);
  14.         
  15.         System.out.println(false^false);
  16.         System.out.println(true^true);
  17.  
  18.     }
  19.  
  20. }

Output:


  1. true
  2. false
  3. false
Program #3: java xor boolean expression and integer : java example program Using Eclipse IDE.

java Xor operator

Java Xor Strings:

  • Gives compile time error.
  • The operator ^ is undefined for the argument type(s) java.lang.String, java.lang.String

Program #4: Java Xor of two strings


  1. package com.Xorinjava;
  2. public class XOR {
  3.     /**
  4.     * Xor in java boolean Xor example program
  5.     * @author www.instanceofjava.com
  6.     */
  7.     public static void main(String[] args) {
  8.         String str="a";
  9.         String str1="b";
  10.         System.out.println(str^str1);// compile time error: The operator ^ is undefined for the
  11. argument type(s) java.lang.String, java.lang.String
  12.  
  13.     }
  14.  
  15. }


 Xor of Binary Strings:

Program #5: Java xor of two binary strings.


  1. package com.Xorinjava;
  2. public class XOR {
  3.     /**
  4.     * Xor in java String bits Xor example program
  5.     * @author www.instanceofjava.com
  6.     */
  7.     public static void main(String[] args) {
  8.         String str1="1010100101";
  9.         String str2="1110000101";
  10.         StringBuffer sb=new StringBuffer();
  11.         
  12.         for (int i = 0; i < str1.length(); i++) {
  13.             
  14.             sb.append(str1.charAt(i)^str2.charAt(i));
  15.             
  16.         }
  17.        System.out.println(sb);
  18.     }
  19.  
  20. }
Output:


  1. 0100100000

Convert arraylist to array in java with example program

Posted by: Instanceofjava Posted date: March 19, 2017 / comment : 1 ,

  • Inoder to convert arraylist to array normally we will try to iterate arraylist using loop and get each element and put it in an array.
  • But you know we have a predefined method in arraylist which convert list to array of elements in sequence order.
  • toArray() method inside arraylist class.



  1. public <T> T[] toArray(T[] a) {  }



  •  Lets see a java program on how to convert arraylist to array.

 Program #1: Java example program to covert arraylist to array using toArray() method


  1. package arraysinterview;
  2. import java.util.ArrayList;
  3. import java.util.List;
  4.  
  5. public class ArrayListTOArray {
  6.  
  7.     public static void main(String[] args) {
  8.         List<String> list = new ArrayList<String>();
  9.         
  10.         list.add("array");
  11.         list.add("arraylist");
  12.         list.add("convertion");
  13.         list.add("javaprogram");
  14.         
  15.         String [] str = list.toArray(new String[list.size()]);
  16.         
  17.         for (int i = 0; i < str.length; i++) {
  18.             System.out.println(str[i]);
  19.         }
  20.  
  21.     }
  22.  
  23. }

Output:
  1. array
  2. arraylist
  3. convertion
  4. javaprogram

Program #2: Java example program to covert Integer arraylist to int array using toArray() method

  •  In this case toArray() method gives Integer array so we need to convert again Integer array to int array.



  1. package arraysinterview;
  2. import java.util.ArrayList;
  3. import java.util.List;
  4.  
  5. public class ArrayListTOArray {
  6.  
  7.  public static void main(String[] args) {
  8.         List<Integer> list = new ArrayList<Integer>();
  9.         
  10.         list.add(10);
  11.         list.add(20);
  12.         list.add(30);
  13.         list.add(40);
  14.         list.add(50);
  15.         
  16.         Object[] integers = list.toArray();
  17.         
  18.         int[] intarray = new int[integers.length];
  19.         int i = 0;
  20.         for (Object n : integers) {
  21.             intarray[i++] = (Integer) n;
  22.             System.out.println(i);
  23.         }
  24.  
  25.     }
  26.  
  27. }



Output:
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5



Finalize() method in java with example program

Posted by: Instanceofjava Posted date: March 19, 2017 / comment : 0

  • finalize() method pre defined method which is present in java.lang.Object class.
  • finalize() method is protected  method defined in java.lang.Object class.
  • The finalize method is a method defined in the Object class in Java. It is called by the garbage collector before an object is garbage collected.
  • The finalize method can be overridden in a subclass to perform any cleanup that is required before the object is garbage collected. For example, if an object has opened a file, it may need to close that file in its finalize method.


  1. protected void finalize() throws Throwable{
  2.  
  3. }



1.What is purpose of overriding finalize() method?

  • The finalize() method should be overridden for an object to include the clean up code or to dispose of the system resources that should to be done before the object is garbage collected.

2.How many times does the garbage collector calls the finalize() method for an object? 

  • Only once.

3.What happens if an uncaught exception is thrown from during the execution of finalize() method of  an object?

  •  The exception will be ignored and the garbage collection (finalization) of that object terminates

  •  If we are overriding finalize() method then its our responsibility to call finalize() method explicitly.

  •  finalize() method never invoked more than once by JVM or any given object.
  • There is no guaranty that if we call finalize() method but we can force garbage collector by calling below two methods
  • System.gc();
  • Runtime.getRuntime().gc();

#1 : Java program to explain about finalize() method


  1. package inheritance
  2. public class B {
  3.  /**
  4.  * Finalize() method in java
  5.  * @author www.instanceofjava.com
  6.  */
  7.   @Override
  8.   protected void finalize() throws Throwable {
  9.             try{
  10.                 System.out.println("Inside Finalize() method of Sub Class : B");
  11.             }catch(Throwable t){
  12.                 throw t;
  13.             }finally{
  14.                 System.out.println("Calling finalize() method of Super Class:  Object");
  15.                 super.finalize();
  16.             }
  17.          
  18.  }
  19.  
  20. public static void main(String[] args) throws Throwable{
  21.         B obj= new B();
  22.         String str=new String("finalize method in java");
  23.         str=null;
  24.         obj.finalize();
  25.         
  26.         }
  27. }

finalize() method in java with example program
  • It is important to note that the finalize method is not guaranteed to be called, and it should not be relied upon for performing important tasks. It is generally better to use try-finally blocks to ensure that resources are properly cleaned up.
Here is an example of how the finalize method can be overridden in a subclass:

finalize method in java

Final method in java with example programs

Posted by: Instanceofjava Posted date: March 19, 2017 / comment : 1

  • If we declare any method as final by placing final keyword then that method becomes final method.
  • The main use of final method in java is they are not overridden.
  • We can not override final methods in sub classes.
  • If we are using inheritance and we need some methods not to overridden in sub classes then we need make it final so that those methods can not be overridden by sub classes. 
  • We can access final methods in sub class but we can not overridden final methods.



Defining a final method in java:

  • Add final keyword to the normal method then it will become final method.
  1. public final void method(){
  2. //code
  3.  }

What happens if we try to override final methods in sub classes?


#1 : Java program to explain about final method in java

  1. package inheritance;
  2. /**
  3.  * final methods in java with example program
  4.  * @author www.instanceofjava.com
  5.  */
  6. public class A {
  7.  
  8.     int a,b;
  9.     
  10.     public final void show(){
  11.         System.out.println("A class show method");
  12.     }
  13. }

final method in java with example program

 Can we access final methods in sub classes?

  • Yes we can access final methods in sub classes.
  • As mentioned above we can access all super class final methods in sub class but we can not override super call final methods.

#2 : Java program to explain about final method in java

  1. package inheritance;
  2. /**
  3.  * final methods in java with example program
  4.  * @author www.instanceofjava.com
  5.  */
  6. public class A {
  7.  
  8.     int a,b;
  9.     
  10.     public final void show(){
  11.         System.out.println("A class show method");
  12.     }
  13. }

  1. package inheritance;
  2.  
  3. /**
  4.  * final methods in java with example program
  5.  * @author www.instanceofjava.com
  6.  */
  7.  
  8. public class B {
  9.     
  10.  public static void main(String[] args){
  11.         
  12.         B obj = new B();
  13.         obj.show();
  14.        
  15.     }
  16. }

Output:
  1. A class show method

Top 10 Java interview questions on final keyword 

Static method vs final static method in java with example programs  

Final static string vs Static string in java  

Format text using printf() method in java

Posted by: Instanceofjava Posted date: March 19, 2017 / comment : 0

printf method in java:

  • Print() and println() methods are used to print text and object values or format data.
  • In order to format text we also have printf() method in java
  • Formatting data means displaying corresponding data type value. 
  • For example when print float ot double value if we want to specify upto 2 decimal numbers we user.
  • System.out.printf("%.2f", variable); 
  • Also alignment of string data. when we are printing string data in java using print() and pintf() 



#1. Write a program to print string using print() and printf() methods


  1. package printfinjava;
  2. /**
  3.  * How to format text using java printf() method
  4.  * @author www.instanceofjava.com
  5.  */
  6.  
  7. public class PrintfMethod {
  8.  
  9.     public static void main(String[] args) {
  10.         String str="java printf double";
  11.         
  12.         System.out.println ("String is "+str);
  13.         System.out.printf ("String is %s", str);
  14.  
  15.     }
  16.  
  17. }
Output:

  1. String is java printf double
  2. String is java printf double

 java printf table

printf in java double int string
Format double using printf():
  • We can format double using printf() method in java
  • format double to 2 decimal places in java possible by using system.out.printf() method.

#2. Write a program to print double to 2 decimal places in java

  1. package printfinjava;
  2. /**
  3.  * How to format text using java printf() method
  4.  * @author www.instanceofjava.com
  5.  */
  6.  
  7. public class PrintfMethod {
  8.  
  9. public static void main(String[] args) {
  10.  
  11.      double value=12.239344;
  12.      System.out.printf("%.2f", value);
  13.  
  14. }
  15.  
  16. }
Output:

  1. 12.24

#3. Write a program to format text using printf() method in java
printf in java double

How to get java source files from jar file

Posted by: Instanceofjava Posted date: November 27, 2016 / comment : 1

  • Jar : Java Archive is a group of .class files.
  • We can create a jar file using following commands
  • jar -cvf  example.jar test.class
  • jar -cvf example.jar *.*
  • To unzip from jar file we need to use following command.
  • jar -xvf  instanceofjava.jar



How to get source code from jar file using java De-compilers

how to get source code from jar file in eclipse


  • Open JD-GUI and File -> open -> open target jar file.
  • It will show java source code.

How to extract java files from jar in eclipse

  •  We can get java source files from jar file by using eclipse also for this we need to add a plugin.
  • Download jar file from http://jd.benow.ca/
  • Unzip it . you will get jd.ide.eclipse.plugin_1.0.0.jar file  and add it to eclipse plugin folder.
  • And restart your eclipse.
  • Add target jar file to a project and now click on the file you will get source code.
  • You can add target jar file using java project->java buildpath -> add external jars option


how to convert jar to java source in eclipse


  • Here i added jstl core jar to eclipse to see java source files.
  • Click on the file now it will show source code 
  • How to extract java files from jar

how to extract java files from jar in eclipse

How to call non static method from static method java

Posted by: Instanceofjava Posted date: September 24, 2016 / comment : 1 ,

  • Class is a template and when we create object instance variables gets memory.
  • If we create two objects variables get memory in two objects. So instance variables gets memory whenever object is created.
  • When we create variables as static , memory will not be created in objects because static means class level and it belongs to class not object but we can access static variables and static methods from objects.
  • Calling static method from non static method in java 
  • In our scenario calling a non static method from static method in java.
  • If we are calling a non static method then we need to use object so that it will call corresponding object non static method.
  • Non static methods will be executed or called by using object so whenever we want to call a non static method from static method we need to create an instance and call that method.
  • If we are calling non static method directly from a static method without creating object then compiler throws an error. 



Program #1: Java example program to call non static method from static method. 


calling non static method from static method.png

  • In the above program we are trying to call non static method of class from a static method so compiler throwing error.
  • Can not make a static reference to the non- static method nonStaticMethod() from the type StaticMethodDemo
  • So without object we can not cal non static method of a class.
  • Check the below example program calling non static method from static method by creating object of that class and on that object calling non static method.

Program #2: Java example program to call non static method from static method.

  1. package com.instanceofjava.staticinterviewquestions;
  2. //www.instanceofjava.com
  3.  
  4. public class StaticMethodDemo {
  5.  
  6.     
  7.     void nonStaticMethod(){
  8.         System.out.println("non static method");
  9.     }
  10.     
  11.     public static void staticMethod(){
  12.         
  13.         new StaticMethodDemo().nonStaticMethod();
  14.     }
  15.     
  16.     
  17.     
  18.     public static void main(String[] args) {
  19.         
  20.         StaticMethodDemo.staticMethod();
  21. }
  22.  
  23. }
   
Output:

  1. non static method

Calling static method from non static method in java

Posted by: Instanceofjava Posted date: September 24, 2016 / comment : 0 ,

  • Static means class level and non static means object level.
  • Non static variable gets memory in each in every object dynamically.
  • Static variables are not part of object and while class loading itself all static variables gets memory.
  • Like static variables we have static methods. Without creating object we can access static methods.
  • Static methods are class level. and We can still access static methods in side non static methods.
  • We can call static methods without using object also by using class name.
  • And the answer to the question of  "is it possible to call static methods from non static methods in java" is yes.
  • If we are calling a static method from non static methods means calling a single common method using unique object of class which is possible. 


Program #1: Java example program to call static method from non static method.


  1. package com.instanceofjava.staticinterviewquestions;
  2. public class StaticMethodDemo {
  3.  
  4. void nonStaticMethod(){
  5.         
  6.         System.out.println("Hi i am non static method");
  7.         staticMethod();
  8.  }
  9.     
  10.  public static void staticMethod(){
  11.         
  12.         System.out.println("Hi i am static method");
  13.   }
  14.     
  15.  public static void main(String[] args) {
  16.         StaticMethodDemo obj= new StaticMethodDemo();
  17.         
  18.         obj.nonStaticMethod();
  19.  
  20.     }
  21.  
  22. }
 Output:

  1. Hi i am non static method
  2. Hi i am static method

  • In the above program we have created object of the class and called a non static method on that object and in side non static method called a static method.
  • So it is always possible to access static variables and static methods in side non static methods

 Program #2: Java example program to call static method from non static method.


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