Java中list根据id获取对象的几种方式

List<Object> list = ...;
int id = ...;
Object result = null;
for (Object obj : list) {
  if (obj.getId() == id) {
    result = obj;
    break;
  }
}

List<Object> list = ...;
int id = ...;
Object result = list.stream().filter(o -> o.getId() == id).findFirst().get();

List<Object> list = ...;
Map<Integer, Object> map = list.stream().collect(Collectors.toMap(Object::getId, o -> o));
int id = ...;
Object result = map.get(id);

package com.web;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class Test4 {
    public static void main(String[] args) {
        // List<String> resultList = new LinkedList<>();结果也一样
        List<String> resultList = new ArrayList<>();
        resultList.add("success");
        resultList.add("error");
        resultList.add("success");
        resultList.add("warn");
        resultList.add("error");
        //1.利用equals,通过循环对比来找出你要的元素如下图所示
        int index = resultList.indexOf("warn");
        System.out.println("index = " + index);
        // index = 3
        System.out.println(resultList.get(index));
        //2.直接get，根据add进去的顺序找出你需要的元素
        for (String s :
                resultList) {
            if (("error").equals(s)) {
                System.out.println(s);
            }
        }
        //3.你也可以通过indexOf(赛选条件)找到元素的下表，然后get出来
       // -1 if this list does not contain the element.
        if (resultList.indexOf("warn") != -1) {
            System.out.println(resultList.get(resultList.indexOf("warn")));
        }
       //使用Iterator迭代器获取
        Iterator it = resultList.iterator();
        while (it.hasNext()){
            String str = (String) it.next();
            if ("success".equals(str)){
                System.out.println("str = " + str);
            }
        }
    }
}