NullPointerException is a runtime exception and it is thrown when the application try to use an object reference which has a null value.For example, using a method on a null reference.Object ref = null; ref.toString(); // this will throw a NullPointerException

From Java 8 onwards, static methods are allowed in Java interfaces.An interface can also have static helper methods from Java 8 onwards. public interface vehicle {    default void print() {       System.out.println("I am a vehicle!");    }    static void blowHorn() {       System.out.println("Blowing horn!!!");    } }Default Method ExampleCreate the following Java program using any editor of your choice in, say, C:\> JAVA.Java8Tester.javaLive Demopublic class Java8Tester {    public static void main(String args[]) {       Vehicle vehicle = new Car(); vehicle.print();    } } interface Vehicle {    default void print() { ... Read More

Let us look at a simple code that will print the words Hello World.ExampleLive Demopublic class MyFirstJavaProgram {    /* This is my first java program. *    This will print 'Hello World' as the output */    public static void main(String []args) {       System.out.println("Hello World"); // prints Hello World    } }Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps −Open notepad and add the code as above.Save the file as: MyFirstJavaProgram.java.Open a command prompt window and go to the directory where you saved the class. Assume ... Read More

Following example helps to determine the rows and columns of a two-dimensional array with the use of arrayname.length.ExampleFollowing example helps to determine the upper bound of a two dimensional array with the use of arrayname.length. public class Main {    public static void main(String args[]) {       String[][] data = new String[2][5];       System.out.println("Dimension 1: " + data.length);       System.out.println("Dimension 2: " + data[0].length);    } }OutputThe above code sample will produce the following result. Dimension 1: 2 Dimension 2: 5

Yes, use String.split() method to do it. See the example below −Examplepublic class Tester {    public static void main(String[] args) {       String text = "This,is,a,comma,seperated,string.";       String[] array = text.split(",");       for(String value:array) {          System.out.print(value + " ");       }    } }OutputThis is a comma seperated string.

You can simply iterate the byte array and print the byte using System.out.println() method.Examplepublic class Tester {    public static void main(String[] args) {       byte[] a = { 1,2,3};       for(int i=0; i< a.length ; i++) {          System.out.print(a[i] +" ");       }    } }Output1 2 3

Yes. Create a list to represent a 2D array and then use Collections.shuffle(list).Exampleimport java.util.ArrayList; import java.util.Collections; import java.util.List; public class Tester {    public static void main(String[] args) {       List rows = new ArrayList();       rows.add(new int[]{1,2,3});       rows.add(new int[]{4,5,6});       rows.add(new int[]{7,8,9});       System.out.println("Before Shuffle");       System.out.println("[0][0] : " + rows.get(0)[0]);       System.out.println("[1][1] : " + rows.get(1)[1]);       System.out.println("After Shuffle");       Collections.shuffle(rows);       System.out.println("[0][0] : " + rows.get(0)[0]);       System.out.println("[1][1] : " + rows.get(1)[1]);    } }OutputBefore Shuffle [0][0] : 1 [1][1] : 5 After Shuffle [0][0] : 7 [1][1] : 2

Following program shows how to initialize an array declared earlier.Examplepublic class Tester {    int a[];    public static void main(String[] args) {       Tester tester = new Tester();       tester.initialize();    }    private void initialize() {       a = new int[3];       a[0] = 0;       a[1] = 1;       a[2] = 2;       for(int i=0; i< a.length ; i++) {          System.out.print(a[i] +" ");       }    } }Output0 1 2

You ByteArrayOutputStream to write byte arrays and get the result using its toByteArray() method.import java.io.ByteArrayOutputStream; import java.io.IOException; public class Tester { public static void main(String[] args) throws IOException { byte[] a = { 1,2,3}; byte[] b = { 4,5,6}; ByteArrayOutputStream baos = new ByteArrayOutputStream(); baos.write(a); baos.write(b); byte[] c = baos.toByteArray(); for(int i=0; i< c.length ; i++){ System.out.print(c[i] +" "); } } }Output1 2 3 4 5 6

If you wish to create a dynamic 2d array in Java without using List. And only create a dynamic 2d array in Java with normal array then click the below linkYou can achieve the same using List. See the below program. You can have any number of rows or columns.Exampleimport java.util.ArrayList; import java.util.List; public class Tester {    public static void main(String[] args) {       List rows = new ArrayList();       rows.add(new int[]{1, 2, 3});       rows.add(new int[]{1, 2});       rows.add(new int[]{1});       //get element at row : 0, column ... Read More