What is the this Keyword in Java?

The this keyword refers to the current object instance. It is used to access instance variables, call other constructors, and pass the current object as a parameter.

1. Refer to Instance Variables

class Student {
    int rollNo;
    String name;
    
    Student(int rollNo, String name) {
        this.rollNo = rollNo;
        this.name = name;
    }
}

2. Call Another Constructor

class Employee {
    int id;
    String name;
    
    Employee(int id, String name) {
        this.id = id;
        this.name = name;
    }
    
    Employee() {
        this(0, "Default");
    }
}

3. Return Current Object

class Calculator {
    int value;
    
    Calculator add(int num) {
        this.value += num;
        return this;
    }
    
    Calculator multiply(int num) {
        this.value *= num;
        return this;
    }
    
    void print() {
        System.out.println("Value: " + value);
    }
}

// Usage
new Calculator().add(5).multiply(2).print();

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