Question

In page 428 (the chapter about Type Information) of his “Thinking In Java, 4th Ed.”, Bruce Eckel has the following example:

public class Staff extends ArrayList<Position> {
    public void add(String title, Person person) {
        add(new Position(title, person));
    }
/* rest of code snipped */

Maybe I’m a bit tired, but I can’t see how the call to add() inside the add() method works. I keep thinking that it should have a reference, or be a static method (and I can’t find a static add() in ArrayList or List). What am I missing?

I just tested for myself, and found that this works:

// Test2.java
public class Test2 {
    public void testMethod() {
        testMethod2();
    }

    public void testMethod2() {
        System.out.println("Here");
    }

    public static void main(String[] args) {
        Test2 t = new Test2();
        t.testMethod();
    }
}

Answer 1

Java implicitly assumes a reference to the current object for methods called like this. So

// Test2.java
public class Test2 {
    public void testMethod() {
        testMethod2();
    }

    // ...
}

Is exactly the same as

// Test2.java
public class Test2 {
    public void testMethod() {
        this.testMethod2();
    }

    // ...
}

I prefer the second version to make more clear what you want to do.