Definition of this:

• this is a reference to the current object that invokes a method.
• Is automatically passed to all methods of a class.

Use of this within methods:

• Allows you to access members (variables and methods) of the current instance.
• this is optional when there is no ambiguity, but necessary to differentiate between local and instance variables with the same name.

Example without this:

class Pwr {
    double b;
    int e;
    double val;

    Pwr(double base, int exp) {
        b = base;
        e = exp;
        val = 1;
        if (exp == 0) return;
        for (; exp > 0; exp--) val = val * base;
    }

    double get_pwr() {
        return val;
    }
}

Explicit use of this:

• Clarifies the code and resolves ambiguity.
• Example of use to resolve name ambiguity:

class Pwr {
    double b;
    int e;
    double val;

    Pwr(double b, int e) {
        this.b = b;
        this.e = e;
        this.val = 1;
        if (e == 0) return;
        for (; e > 0; e--) this.val = this.val * b;
    }

    double get_pwr() {
        return this.val;
    }
}

When to use this:
Useful for accessing instance variables when names conflict with local variables or parameters.
In constructor methods, to reference the object under construction.

class Pwr {
    double b;
    int e;
    double val;

    Pwr(double base, int exp) {
        this.b = base;
        this.e = exp;
        this.val = 1;
        if (exp == 0) return;
        for (; exp > 0; exp--) this.val = this.val * base;
    }

    double get_pwr() {
        return this.val;
    }
}

class DemoPwr {
    public static void main(String args[]) {
        Pwr x = new Pwr(4.0, 2);
        Pwr y = new Pwr(2.5, 1);
        Pwr z = new Pwr(5.7, 0);
        System.out.println(x.b   " raised to the "   x.e  
            " power is "   x.get_pwr());
        System.out.println(y.b   " raised to the "   y.e  
            " power is "   y.get_pwr());
        System.out.println(z.b   " raised to the "   z.e  
            " power is "   z.get_pwr());
    }
}

Explanation:

• The Pwr class calculates the power of a number.
• The use of this is demonstrated to reference instance variables when the method parameters have the same name.