HashSet (需要重寫hashCode和equals方法)
阿新 • • 發佈:2019-01-10
一般描述的事物需要往集合中新增,那麼都需要重寫這兩個方法
刪除和判斷元素是否存在,都是先判斷hashCode 看看是否存在,若存在則繼續equals();
import java.util.*; class Person { private String name; private int age; Person(String name,int age) { this.name=name; this.age=age; } public int hashCode()//重寫 { return name.hashCode()+age ; } public boolean equals(Object obj)//重寫 Object不能換 { if(!(obj instanceof Person)) return false; Person p=(Person)obj; System.out.println(this.name+"...."+p.name); return this.name.equals(p.name)&&this.age==p.age; } public String getName() { return name; } public int getAge() { return age; } } class HashSetDemo { public static void main(String[] args) { HashSet hs=new HashSet(); hs.add(new Person("lisi01",30)); hs.add(new Person("lisi02",33)); hs.add(new Person("lisi03",35)); hs.add(new Person("lisi02",33)); hs.add(new Person("lisi01",30)); hs.add(new Person("lisi04",32)); hs.add(new Person("lisi03",35)); Iterator it=hs.iterator(); while(it.hasNext()) { Person p=(Person)it.next();; sop(p.getName()+" "+p.getAge()); } } public static void sop(Object obj) { System.out.println(obj); } }