What does the this keyword mean in Java, and where do you use it?

When you say "my phone" you mean the phone of whoever is speaking. Inside a method, this works the same way: it points to the object that was used to call the method.

Three common uses: (1) this.name = name tells the compiler the left side is the field and the right side is the parameter; (2) this(...) calls another constructor of the same class; (3) return this or list.add(this) hands the current object to someone else.

class Account {
    private String owner;
    private double balance;

    Account(String owner) { this(owner, 0); }      // calls the other constructor

    Account(String owner, double balance) {
        this.owner = owner;                        // field = parameter
        this.balance = balance;
    }

    Account deposit(double amt) {
        balance += amt;
        return this;                               // allows chaining
    }
}

new Account("Meera").deposit(500).deposit(250);

this(...) must be the first statement in the constructor. this does not exist in static methods because no object is involved.

• Writing name = name in a constructor. That assigns the parameter to itself and leaves the field at its default.
• Trying to use this inside a static method.