You can declare an array just like a variable −int myArray[];You can create an array just like an object using the new keyword −myArray = new int[5];You can initialize the array by assigning values to all the elements one by one using the index −myArray [0] = 101; myArray [1] = 102;You can access the array element using the index values −System.out.println("The first element of the array is: " + myArray [0]); System.out.println("The first element of the array is: " + myArray [1]); Alternatively, you can create and initialize an array using the flower braces ({ }): Int [] myArray = {10, 20, 30, 40, 50}

You can call one constructor from another using this(). Example This is a default constructor This is parameterized constructor Live Demo public class Sample { int num; public Sample() { System.out.println("This is default constructor"); num = 30; } public Sample(int value) { this(); System.out.println("This is parameterized constructor"); num = value; } public static void main(String args[]){ Sample s = new Sample(30); } } Output This is default constructor This is parameterized constructor

You can declare an array just like a variable −int myArray[];You can create an array just like an object using the new keyword −myArray = new int[5];You can initialize the array by assigning values to all the elements one by one using the index −myArray [0] = 101; myArray [1] = 102;You can access the array element using the index values −System.out.println("The first element of the array is: " + myArray [0]); System.out.println("The first element of the array is: " + myArray [1]); Alternatively, you can create and initialize an array using the flower braces ({ }): Int [] myArray = {10, 20, 30, 40, 50}

The composition is also a type of aggregation where the relationship is restrictive i.e. If two objects are in composition, the composed object will not exist without the other.

While declaring the constructors you should keep the following points in mind.A constructor does not have a return type.The name of the constructor is same as the name of the class. A class can have more than one constructor.Examplepublic class Sample {    int num;    public Sample() {       num = 30;    }    public Sample(int value) {       num = value;    } }

When an object A contains a reference to another object B or we can say Object A has a HAS-A relationship with Object B, then it is termed as Aggregation. Aggregation helps in reusing the code. Object B can have utility methods and which can be utilized by multiple objects. Whichever class has object B then it can utilize its methods. Example public class Vehicle{} public class Speed{} public class Van extends Vehicle { private Speed sp; } This shows that class Van HAS-A Speed. By having a separate class for Speed, we do ... Read More

A singleton class in Java is the one which can have only one object.The easiest implementation consists of a private constructor and a field to hold its result, and a static accessor method with a name like getInstance(). The private field can be assigned from within a static initializer block or, more simply, using an initializer. The getInstance( ) method (which must be public) then simply returns this instance −Examplepublic class Singleton {    private static Singleton singleton = new Singleton(); private Singleton() { }        public static Singleton getInstance() {       return singleton;    } ... Read More

The this is a keyword in Java which is used as a reference to the object of the current class, within an instance method or a constructor. Using this you can refer the members of a class such as constructors, variables, and methods. Example Live Demo public class This_Example { // Instance variable num int num = 10; This_Example() { System.out.println("This is an example program on keyword this"); } This_Example(int num) { ... Read More

A Java file contains only one public class with a particular name. If you create another class with same name it will be a duplicate class. Still if you try to create such class then the compiler will generate a compile time error. Example public class Example { } public class Example{ public void sample(){ System.out.println("sample method of the Example class"); } public void demo(){ System.out.println("demo method of the Example class"); } ... Read More

This is a static method of the class named Integer it accepts an integer parameter and Parses it as a signed decimal integer. Example Live Demo public class IntegerDemo { public static void main(String[] args) { // parses the string argument int a = Integer.parseInt("12"); int b = Integer.parseInt("26"); int c = Integer.parseInt("54"); int m = a * b * c; System.out.print("Value after multiplying = " + m); } } Output Value after multiplying = 16848