this.java

package com.example;

// Normally you would put each of these classes in their own file

class Point {

    static final Point ORIGIN = new Point(0, 0);
    private final double x;
    private final double y;

    public Point(final double x, final double y) {
        // a good example of 'this'
        this.x = x;
        this.y = y;
    }

    public double getX() {
        return x;
    }

    public double getY() {
        return y;
    }
}

abstract class Asset {

    private Point mCenter;

    public Asset() {
        // 'this' is used to call the other constructor
        this(Point.ORIGIN);
    }

    public Asset(final Point center) {
        // 'this' is avoided by prefixing members with 'm'
        mCenter = center;
    }

    public Point getCenter() {
        return mCenter;
    }

    public void setCenter(final Point center) {
        mCenter = center;
    }

    public abstract void draw();

}

class Rectangle extends Asset {

    private double mWidth;
    private double mHeight;

    public Rectangle() {
        this(Point.ORIGIN, 0, 0);
    }

    public Rectangle(final Point center, final double width, final double height) {
        // 'super' is like 'this', but refers to the superclass (Asset in this case)
        super(center);
        mWidth = width;
        mHeight = height;
    }

    @Override
    public void draw() {
        // do the drawing
    }

    public double getWidth() {
        return mWidth;
    }

    public void setWidth(final double width) {
        mWidth = width;
    }

    public double getHeight() {
        return mHeight;
    }

    public void setHeight(final double height) {
        mHeight = height;
    }
}

interface IRectangleBuilder {

    RectangleBuilder setCenter(final Point center);

    RectangleBuilder setWidth(final double width);

    RectangleBuilder setHeight(final double height);

    Rectangle build();
}

class RectangleBuilder implements IRectangleBuilder {

    protected Rectangle mRectangle;

    public RectangleBuilder() {
        mRectangle = new Rectangle();
    }

    @Override
    public RectangleBuilder setCenter(final Point center) {
        mRectangle.setCenter(center);
        // return the instance of this rectangle so we can chain methods
        return this;
    }

    @Override
    public RectangleBuilder setWidth(final double width) {
        mRectangle.setWidth(width);
        return this;
    }

    @Override
    public RectangleBuilder setHeight(final double height) {
        mRectangle.setHeight(height);
        return this;
    }

    @Override
    public Rectangle build() {
        return mRectangle;
    }
}

class Test {

    static {
        Rectangle rectangle = new RectangleBuilder()
                .setCenter(new Point(10, 20))
                .setWidth(100)
                .setHeight(200)
                .build();
        rectangle.draw();
    }
}

// Don't do this, it's confusing
class Outer {

    Object mObj;

    class Inner {

        Object mObj;

        Object getOuterObj() {
            return Outer.this.mObj;
        }

        Outer getOuter() {
            return Outer.this;
        }
    }
}