遍历map及List集合的方法


import com.xinji.dto.UserDTO;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * @Author:ella on 2020/1/15.
 */
public class TestInterator {

    //遍历List集合的方法

    //1.foreach方法
    public void iteratorList1(ArrayList<UserDTO> arrayList) {
        for (UserDTO userDTO : arrayList) {
            System.out.println("jira:" + userDTO.getJiraNo() + ",cardNo:" + userDTO.getCardNo() + ",gender:" + userDTO.getGender());
        }
    }

    //2.list.get()方法
    public void iteratorList2(ArrayList<UserDTO> arrayList) {
        for (int i = 0; i < arrayList.size(); i++) {
            UserDTO userDTO = arrayList.get(i);
            System.out.println("jira:" + userDTO.getJiraNo() + ",cardNo:" + userDTO.getCardNo() + ",gender:" + userDTO.getGender());
        }
    }

    //3.Iterator方法
    public void iteratorList3(ArrayList<UserDTO> arrayList) {
        Iterator<UserDTO> iterator = arrayList.iterator();
        while (iterator.hasNext()) {
            UserDTO userDTO = iterator.next();
            System.out.println("jira:" + userDTO.getJiraNo() + ",cardNo:" + userDTO.getCardNo() + ",gender:" + userDTO.getGender());
        }
    }


    public static void main(String[] args) {
        ArrayList<UserDTO> list = new ArrayList<>();
        list.add(new UserDTO("001", "1000002021129921001", "男"));
        list.add(new UserDTO("002", "1000002021129921002", "女"));
        list.add(new UserDTO("003", "1000002021129921003", "男"));
        list.add(new UserDTO("004", "1000002021129921004", "女"));

        TestInterator testInterator = new TestInterator();

        System.out.println("############1");
        testInterator.iteratorList1(list);

        System.out.println("############2");
        testInterator.iteratorList2(list);

        System.out.println("############3");
        testInterator.iteratorList3(list);
    }

}

package com.iat.InvalidCases;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * @Author:ella on 2020/1/15.
 */
public class TestInterator {


    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("key1", "value1");
        map.put("key2", "value2");
        map.put("key3", "value3");
        TestInterator interator = new TestInterator();

        System.out.println("###############1");
        interator.iteratorMap1(map);

        System.out.println("###############2");
        interator.iteratorMap2(map);

        System.out.println("###############3");
        interator.iteratorMap3(map);
    }

    //遍历map的方法
    public void iteratorMap1(Map<String, String> map) {
        // 1. entrySet遍历，在键和值都需要时使用（最常用）
        for (Map.Entry<String, String> entry : map.entrySet()) {
            System.out.println("key = " + entry.getKey() + ", value = " + entry.getValue());
        }
    }

    public void iteratorMap2(Map<String, String> map) {
        // 2. 通过keySet或values来实现遍历,性能略低于第一种方式
        for (String key : map.keySet()) {
            System.out.println("key = " + key);
            System.out.println("value = " + map.get(key));
        }

        for (String value : map.values()) {
            System.out.println("value = " + value);
        }
    }


    public void iteratorMap3(Map<String, String> map) {
        // 3. 使用Iterator遍历
        Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<String, String> entry = it.next();
            System.out.println("key = " + entry.getKey() + ", value = " + entry.getValue());
        }
    }

}

来源：CSDN

作者：毛依依

链接：https://blog.csdn.net/baidu_15873551/article/details/103994219

标签

string

遍历map

arraylist