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Benefits of arraylist in java over arrays

Posted by: Instanceofjava Posted date: 1:10 PM / comment : 0 java Collections interview Questions , java programming interview questions

Disadvantages of arrays:

Check the disadvantages of arrays in below article.
Advantages and disadvantages of arrays in java

Advantages / Benefits of arraylist in java:

We have some disadvantages of arrays like arrays are fixed in length. and we need to mention size of the array while creation itself.
So we have some advantages of arraylist when compared to arrays in java.
Here the major advantages of arraylist over arrays.

1.ArrayList is variable length

One of the major benefit of arraylist is it is dynamic in size. we can increase as well as decrease size of the arraylist dynamically.
Resizable.

Program #1: Java example program to explain the advantages of ArrayList: resizable

package collections;
import java.util.ArrayList;
public class ArrayListExample {
/**
* Advantages of arrayList over arrays in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(1);
list.add(2);
list.add(3);
System.out.println(list.size());
list.add(4);
list.add(5);
System.out.println(list.size());
list.remove(1);
System.out.println(list.size());
}
}

Output:

In the above program by using add and remove methods of ArrayList we can change the size of the ArrayList

2.Default initial capacity is 10.

One of the major benefit of arraylist is by default it will assign default size as 10.
Whenever we create object of ArrayList constructor of ArrayList assign default capacity as 10.

3.Insert and remove elements also at particular position of ArrayList

Another advantage of ArrayList is it can add and remove elements at particular position.

Program #2: Java example program to explain the advantages of ArrayList:Add and remove elements at particular position.

package collections;
import java.util.ArrayList;
public class ArrayListExample {
/**
* Advantages of arrayList over arrays in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(1);
list.add(2);
list.add(3);
System.out.println(list);
list.add(0,4);
System.out.println(list);
list.add(2,5);
System.out.println(list);
list.remove(3);
System.out.println(list);
System.out.println(list.size());
}
}

Output:

[1, 2, 3]
[4, 1, 2, 3]
[4, 1, 5, 2, 3]
[4, 1, 5, 3]
4

4.Add any type of data into ArrayList.

We can add different type of objects in to the ArrayList.
In this scenario avoid mentioning generics while declaring ArrayList.

Program #3: Java example program to explain the advantages of ArrayList: Add any type of Object.

5.Traverse in both directions.

We can traverse both direction using List Iterator.

Program #4: Java example program to explain the advantages of ArrayList: Traverse in both directions.

package collections;
import java.util.ArrayList;
import java.util.ListIterator;
public class ArrayListExample {
/**
* Advantages of arrayList over arrays in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
ArrayList<String> list = new ArrayList<String>();
list.add("ArrayList Advantages");
list.add("ArrayList benefits");
list.add("ArrayList in java");
ListIterator iterator = list.listIterator();
System.out.println("**ArrayList Elements in forward direction**");
while (iterator.hasNext())
{
System.out.println(iterator.next());
}
System.out.println("**ArrayList Elements in backward direction**");
while (iterator.hasPrevious())
{
System.out.println(iterator.previous());
}
}
}

Output:

**ArrayList Elements in forward direction**
ArrayList Advantages
ArrayList benefits
ArrayList in java
**ArrayList Elements in backward direction**
ArrayList in java
ArrayList benefits
ArrayList Advantages

6.ArrayList allows Multiple null values

We can add multiple null elements to ArrayList

Program #5: Java example program to explain the benefits of ArrayList: Add null elements

package collections;
import java.util.ArrayList;
public class ArrayListExample {
/**
* Advantages of arrayList over arrays in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
ArrayList<String> arraylist = new ArrayList<String>();
arraylist.add(null);
arraylist.add(null);
arraylist.add(null);
System.out.println(arraylist);
}
}

Output:

[null, null, null]

7.ArrayList allows to add duplicate elements

We can add duplicate elements into arrayList

Program #6: Java example program to explain the advantages of ArrayList: Add any type of Object.

package collections;
import java.util.ArrayList;
public class ArrayListExample {
/**
* Advantages of arrayList over arrays in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
ArrayList<String> arraylist = new ArrayList<String>();
arraylist.add("ArrayList");
arraylist.add("ArrayList");
arraylist.add("ArrayList");
System.out.println(arraylist);
}
}

Output:

[ArrayList, ArrayList, ArrayList]

8.ArrayList has many methods to manipulate stored objects.

ArrayList has many methods to manipulate stored objects.
addAll(), isEmpty(). lastIndexOf() etc.

Advantages and disadvantages of arrays in java

Posted by: Instanceofjava Posted date: 11:58 AM / comment : 2 Core java Interview Questions , java programming interview questions

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().

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:

Here is the all possible ways of printing arrays in java.
5 Different ways to print arrays in java

Creating array of objects in java:

We can create array of objects in java.
Check out this interesting article about array of objects in java computer programming.
Creating array of objects in java example program

Java program to find missing numbers in an array:

We can find missing numbers in java array lets see the below example program.
Java Program to find missing numbers in an array

Find second highest number in java arrays:

Check this below post about how to find second highest number in an array.
Find second highest number in an integer Array

Convert arrayList to array:

Converting arraylist to array

Copy all elements of hash set to Object array:

Java program to Copy all elements of Java HashSet to an Object Array

Java xor operator with example programs

Posted by: Instanceofjava Posted date: 6:13 PM / comment : 0 Core java Interview Questions

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:

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

package com.Xorinjava;
public class XOR {
/**
* Xor in java Xor example program
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
int a=1;
int b=0;
int c= a^b;
System.out.println(c);
}
}

Output:

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

package com.Xorinjava;
public class XOR {
/**
* Xor in java boolean Xor example program
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
boolean a=true;
boolean b=false;
boolean c= a^b;
System.out.println(c);
System.out.println(false^false);
System.out.println(true^true);
}
}

Output:

true
false
false

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

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

package com.Xorinjava;
public class XOR {
/**
* Xor in java boolean Xor example program
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
String str="a";
String str1="b";
System.out.println(str^str1);// compile time error: The operator ^ is undefined for the
argument type(s) java.lang.String, java.lang.String
}
}

Xor of Binary Strings:

Program #5: Java xor of two binary strings.

package com.Xorinjava;
public class XOR {
/**
* Xor in java String bits Xor example program
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
String str1="1010100101";
String str2="1110000101";
StringBuffer sb=new StringBuffer();
for (int i = 0; i < str1.length(); i++) {
sb.append(str1.charAt(i)^str2.charAt(i));
}
System.out.println(sb);
}
}

Output:

0100100000

How to get first two characters of a string in java

Posted by: Instanceofjava Posted date: 3:15 PM / comment : 2 java string interview programs

We can get first two character of a string in java by using subString() method in java
To get first N numbers of a string s.substring(0,n);
Lets see an example java program on how to get first two characters or first N characters.

In Java, you can use the charAt() method to get the first character of a string. The charAt() method takes an index as a parameter and returns the character at that index.

To get the first character of a string, you can pass in the index 0 to the charAt() method.

Here's an example:

String str = "Hello, World!";

char firstChar = str.charAt(0);

System.out.println("First character: " + firstChar);

This will output:

First character: H

Program #1: Java Program to get first two characters of a String.

package StringInterviewprograms;
public class GetFirstTwoCharacters {
/**
* How to get First N characters in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
String str="Get first two characters of a String";
System.out.println(str.substring(0,2));
}
}

Output:

Program #2:

package StringInterviewprograms;
import java.util.Scanner;
public class GetFirstTwoCharacters {
/**
* How to get First N characters in java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
Scanner sc= new Scanner(System.in);
System.out.println("Please Enter a String");
String str=sc.next();
if(str.length()>=2){
System.out.println(str.substring(0,2));
}else{
System.out.println("please enter a string with minimum length of 2.");
}
}
}

Output:

Please Enter a String
miss you
mi

How to check if a character is a special character in java

Posted by: Instanceofjava Posted date: 12:47 PM / comment : 0 java string interview programs

To check if string contains special character or not or check whether first character is special character or not we can use regex or contains method of sting class.
By using java.util.regex.Matcher class and java.util.regex.Pattern class methods we can check whether string has special character or not
Lets see an example program on how to check a string has special character or not using java regex.

Program #1: Java example program to check string has special character or not using java regex's?

package StringInterviewprograms;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CheckSpecialCharacterString {
/**
* Check whether the String contains special character or not using java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
String Str="Java String interview questions ";
String Str1="Java String interview questions % ";
Pattern p = Pattern.compile("[^a-z0-9 ]", Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(Str);
boolean check = m.find();
if (check)
System.out.println("String: "+Str+" contains special character");
else
System.out.println("String: "+Str+" does not contains any special character");
Matcher m1= p.matcher(Str1);
boolean flag = m1.find();
if(flag)
System.out.println("String: "+Str1+" contains special character");
else
System.out.println("String: "+Str1+" does not contains any special character");
}
}

Output:

String: Java String interview questions does not contains any special character
String: Java String interview questions % contains special character

We can check each character of a string is special character or not without using java regex's.
By using String class contains method and for loop we can check each character of a sting is special character or not.
Let us see a java example program on how to check each character (including space) of a string is special character or not.
String validation for special characters.

Program #2: Java example program to check each character of string is special character or not without using java regex's?

package StringInterviewprograms;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CheckSpecialCharacterString {
/**
* Check whether the each character of String is special character or not using java
* @author www.instanceofjava.com
*/
public static void main(String[] args) {
String Str="Java String interview questions*$%";
String specialCharacters=" !#$%&'()*+,-./:;<=>?@[]^_`{|}";
for (int i = 0; i < Str.length(); i++) {
if (specialCharacters.contains(Character.toString(Str.charAt(i))))
{
System.out.println(Str.charAt(i)+": is a special character");
}
}
}
}

Output:

: is a special character
: is a special character
: is a special character
*: is a special character
$: is a special character
%: is a special character

Program #3: Java example program to check each character of string is special character or not without using java regex's Using Eclipse IDE.

How to check if first character of a string is a number or not in java

Posted by: Unknown Posted date: 12:03 PM / comment : 0 java string interview programs

To check if first character of a string is a number or not in java we can check in multiple ways.
By using Character.isDigit() method by passing character of string using for loop or substring method.
Other way is to check str.substring(0, 1).matches("[0-9]").
Lets see an example program in java to check first character of a string is digit or character.

Program #1: Java example program to check the each character of string is number or not character is a letter or number in Java without using regexes?

package StringInterviewprograms;
/**
* Check whether the given character is a number /digit or not by using java character isdigit
*method
* @author www.instanceofjava.com
*/
public class CheckEachCharacterNumberOrNot {
public static void main(String[] args) {
String str = "instanceofjava37";
//Check whether the given character is a number /digit or not ?
for(int i=0; i<str.length();i++)
{
Boolean flag = Character.isDigit(str.charAt(i));
if(flag){
System.out.println("'"+str.charAt(i)+"' is a number");
}
else{
System.out.println("'"+str.charAt(i)+"' is not a number");
}
}
}
}

Output:

'i' is not a number
'n' is not a number
's' is not a number
't' is not a number
'a' is not a number
'n' is not a number
'c' is not a number
'e' is not a number
'o' is not a number
'f' is not a number
'j' is not a number
'a' is not a number
'v' is not a number
'a' is not a number
'3' is a number
'7' is a number

Program #2: Java example program to check the First character of string is number or not by using regex.

package StringInterviewprograms;
/**
* Check whether the given character is a number /digit or not
* @author www.instanceofjava.com
*/
public class CheckFirstCharacterNumberOrNot {
public static void main(String[] args) {
String str = "instanceofjava37";
Boolean flag1 = str.substring(0, 1).matches("[0-9]");
if(flag1){
System.out.println("First Character is a number..!");
}
else{
System.out.println("First character is not a number..!");
}
}
}

Output:

First character is not a number..!

Program #3: Java example program to check the First character of string is number or not using eclipse IDE.

Check first character string number digit java

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