App.java

package x.y.z;

import java.util.HashMap;
import java.util.Map;

/**
 * Hello world!
 *
 */
public class App {
	public static void main(String[] args) {
		new App().f();
	}
	
	public void f() {
		Map<A, String> map = new HashMap<A, String>();
		A a = new A(3);
		map.put(a, "value");
		System.out.println(map.get(a));
		a.setI(4);
		System.out.println(map.get(a));
		a.setI(3);
		System.out.println(map.get(a));
	}
	
	private class A {
		
		private int i;
		
		public A(int i) {
			this.i = i;
		}
		
		public void setI(int i) {
			this.i = i;
		}
		
		@Override
		public int hashCode() {
			final int prime = 31;
			int result = 1;
			result = prime * result + getOuterType().hashCode();
			result = prime * result + i;
			return result;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			A other = (A) obj;
			if (!getOuterType().equals(other.getOuterType()))
				return false;
			if (i != other.i)
				return false;
			return true;
		}

		private App getOuterType() {
			return App.this;
		}
		
	}
	
}