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最新推荐文章于 2024-04-22 16:59:44 发布

wangxy799

最新推荐文章于 2024-04-22 16:59:44 发布

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分类专栏： java基础文章标签： java面试

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本文介绍了一种使用Java从List集合中去除重复对象的方法。通过将List转换为HashSet，可以高效地移除所有重复元素，并保持唯一项。示例代码展示了如何操作字符串数组并将其转换为List，然后应用此技巧。

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快速从list集合中去除重复的对象

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

//从List集合中去除重复对象
public class DistinctList {
    public static void main(String[] args) {
        String[] ar1 = { "8", "8", "9", "9" ,"0","9"};
        String[] ar2 = { "张三", "张三", "李四", "张三", "王五", "李四" };
        String[] ar3 = { "A", "A", "C", "A", "C", "D" };
        String[] ar4 = { "12", "18", "19", "19", "10", "19" };

        List<String> list = new ArrayList<String>();
        Collections.addAll(list, ar1);
        //List<String> list = Arrays.asList(ar2);

        test1(list);

    }

    public static void test1(List list){
        print(list);
        Set set = new HashSet(list);
        System.out.println("==================");
        print(set);
    }

    public static void print(Collection coll){
        Iterator iterator = coll.iterator(); 
        while(iterator.hasNext()){ 
            String i = (String)iterator.next();                   
            System.out.println(i);   

        }  
    }
}

    SELECT * FROM A A1 WHERE IS EXISTS(SELECT 1 FROM A A2 WHERE A1.NAME=A2.NAME AND A1.ID>A2.ID);