java中set集合如何去除重複元素

set集合是可以重複的元素集合;
用set集合添加一個學生對象元素時:

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

public class People {
    String name;
    int ages;

    public People(String name, int ages) {
        this.name = name;
        this.ages = ages;
    }

    public static void main(String[] args) {
        //創建集合對象
        Set study = new HashSet();
        //List  study=new ArrayList();
        study.add(new People("張三", 45));
        study.add(new People("李四", 37));
        study.add(new People("王五", 54));
        study.add(new People("張三", 45));
        study.add(new People("張三", 25));
        //創建迭代器對象
        Iterator it = study.iterator();
        while (it.hasNext()) {
            People str = (People) it.next();
            System.out.println(str.toSring());
        }
    }
    //重寫頭String方法,使輸出的樣式按照自己所定義的格式輸出
    public String toSring() {
        return name + " " + ages;
    }
}

此時的運行結果:

如何除去重複的元素信息呢?
需要重寫equals()和hashCode()方法;
代碼如下

public class People {
    String name;
    int ages;
    public People(String name, int ages) {
        this.name = name;
        this.ages = ages;
    }
    public static void main(String[] args) {
        //創建集合對象
        Set study = new HashSet();
        //List  study=new ArrayList();
        study.add(new People("張三", 45));
        study.add(new People("李四", 37));
        study.add(new People("王五", 54));
        study.add(new People("張三", 45));
        study.add(new People("張三", 25));
        //創建迭代器對象
        Iterator it = study.iterator();
        while (it.hasNext()) {
            People str = (People) it.next();
            System.out.println(str.toSring());
        }
    }
    public String toSring() {
        return name + " " + ages;
    }
    //重寫equals()方法:判斷姓名和年齡兩者是否都相同;
    @Override
    public boolean equals(Object obj) {
        People p = (People) obj;
        return p.name == this.name && p.ages == this.ages;
    }
    //重寫hashcode()方法:
    @Override
    public int hashCode() {
        return name.hashCode();
    }
}

運行結果:

通過以上代碼,就可以出去set集合中的重複元素!

希望對大家有所幫助!