Java: Classes & Objects

In Java, a class is a blueprint or a template that defines the behavior and properties of objects. An object is an instance of a class, which is created using the new keyword.

To define a class in Java, you use the class keyword, followed by the name of the class, and then the body of the class enclosed in curly braces. For example:

public class MyClass {
    // instance variables
    private int x;
    private String name;

    // constructor
    public MyClass(int x, String name) {
        this.x = x;
        this.name = name;
    }

    // methods
    public int getX() {
        return x;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

In this example, MyClass is a class with two instance variables (x and name), a constructor that takes two arguments to initialize these variables, and three methods (getX, getName, and setName).

To create an object of this class, you use the new keyword and call the constructor with the appropriate arguments. For example:

MyClass obj = new MyClass(42, "John");

This creates a new object of type MyClass with x initialized to 42 and name initialized to “John”. You can then call the methods on this object, for example:

System.out.println(obj.getX()); // prints 42
System.out.println(obj.getName()); // prints "John"
obj.setName("Jane");
System.out.println(obj.getName()); // prints "Jane"

This is just a simple example, but in practice, classes and objects are used extensively in Java to create complex software systems.