java程序语言Set集合方法演示

java程序语言Set集合方法演示

import java.util.Collection;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class HashSetDemos
{

	public static void main(String[] args)
	{
		// 新建一个Set类的集合
		Set   st = new HashSet();
		st.add("abc1");
		st.add("abc2");
		st.add("abc1");
		st.add("abc2");
		//输出结果只会有 abc1  和abc2  不允许元素重复
		Iterator it = st.iterator();
		while(it.hasNext())
		{
			System.out.println(it.next());
		}
		st.removeAll(st);
		st.add(new Studenti("lisi",23));
		st.add(new Studenti("lisi",24));
		st.add(new Studenti("lisan",22));
		st.add(new Studenti("lisan",20));
		Iterator its = st.iterator();
		while(its.hasNext())
		{
			Studenti s = (Studenti) its.next();
			System.out.println(s.getName()+"  "+s.getAge());
		}
	}
}
class Studenti
{
	private String name;
	private int age;
	Studenti(String name ,int age)
	{
		this.name=name;
		this.age = age;
	}
	public int getAge()
	{
		return age;

	}
	public String getName()
	{
		return name;

	}
	public String toString()
	{
		return "the student name : +name "+"  and  age is : "+ age;

	}
	public int hashCode()
	{
		return name.hashCode()+age*10;

	}
	public boolean equals(Object obj)
	{
		 if(this == obj)
             return true ;//同一个对象放两次，直接返回true

       if(!(obj instanceof Studenti))
             throw new ClassCastException("类型错误");

       Studenti p = (Studenti)obj;

       return this .name.equals(p.name) && this.age == p.age;
	}
	}

运行程序：