mutableelement.java

高质量Java程序设计 源代码

package net.betterjava.collection.set;
import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;

class Element {
	int value;

	public Element(int i) {
		super();
		value = i;
	}

	public int getValue() {
		return value;
	}

	public void setValue(int value) {
		this.value = value;
	}

	public boolean equals(Object o) {
		if (o == this)
			return true;

		if (!(o instanceof Element))
			return false;

		return this.value == ((Element) o).getValue();
	}

	public int hashCode() {
		int result = 37;
		return 37 + result + value;
	}

	public String toString() {
		return String.valueOf(value);
	}

}

public class MutableElement {

	public static void main(String[] args) {
		Set aSet = new HashSet();
		Element e1 = new Element(1);
		Element e2 = new Element(2);
		Element e3 = new Element(3);
		aSet.add(e1);
		aSet.add(e2);
		aSet.add(e3);

		System.out.println(e2.equals(e3));

		for (Iterator it = aSet.iterator(); it.hasNext();)
			System.out.println(it.next());

		//modify the third element equals to second element
		e3.setValue(2);

		System.out.println(e2.equals(e3));

		for (Iterator it = aSet.iterator(); it.hasNext();)
			System.out.println(it.next());
	}
}