基于hash的map也是这种机制。

HashSet

import java.util.HashSet;import java.util.Set;import java.util.TreeSet;public class Sets {    public static void main(String[] args) {        // TODO Auto-generated method stub        Person p1 = new Person("320321");        p1.setAge(22);        p1.setName("p1");        Person p2 = new Person("320321");        p2.setAge(23);        p2.setName("p2");        Person p3 = new Person("320322");        p3.setAge(22);        p3.setName("p3");        Person p4=new Person("320321");        p4.setAge(22);        p4.setName("p4");        HashSet
     
       hashSet = new HashSet();        /*         * Add elements         */        // p1 equals p2, p1.hashCode != p2.hashCode        hashSet.add(p1);        hashSet.add(p2);        // p1, p2        System.out.println(hashSet);        // p3 not equals p1, p2, but p3.hashCode == p1.hashCode        hashSet.add(p3);        // p1, p3, p2        System.out.println(hashSet);        // p4 equals p1, p2, and p4.hashCode == p1.hashCode        hashSet.add(p4);        // p1, p3, p2, without p4        System.out.println(hashSet);                /*         * Remove elements. Now, the SET contains p1, p3, p2         */        hashSet.remove(p4);        // p1 will be removed, since p1 equals p4 and p1.hashCode == p4.hashCode        System.out.println(hashSet);        // Although the SET contains p2 who equals p4, but can't find "p4"        // Also, p3.hashCode == p4.hashCode but not find "p4" in the same bucket        System.out.println(hashSet.contains(p4));    }}
     

Person

public class Person implements Comparable
     
       {    private String name, id, gender;    private int age;    private String[] property;    public Person() {    }    public Person(String id) {        this.id = id;    }    public String getId() {        return id;    }    public void setName(String name) {        this.name = name;    }    public void setGender(String gender) {        this.gender = gender;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public String getGender() {        return gender;    }    public int getAge() {        return age;    }    public String[] getProperty() {        return property;    }    public void setProperty(String[] property) {        this.property = property;    }    @Override    public boolean equals(Object o) {        if (this == o) {            return true;        }        if (!(o instanceof Person)) {            return false;        }        Person p = (Person) o;        if (id == null ? p.getId() == null : id.equals(p.getId())) {            return true;        }        return false;    }    @Override    public int hashCode() {        return age;    }    @Override    public String toString() {        return this.id + "  age:  " + this.age + "  name:  " + this.name;    }    @Override    public Person clone() {        Person p = null;        try {            p = (Person) super.clone();            p.setProperty(property.clone());        } catch (CloneNotSupportedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return p;    }    @Override    public int compareTo(Person p) {        return this.age - p.getAge();    }}