史上最全HashMap遍历方式

java Hashmap Map TreeMap 的几种遍历方式,全网最全,全网最强

package Collec2;

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

public class Test1 {

    public static void main(String[] args) {
        HashMap<Student, String> hashmap_88 = new HashMap<Student, String>();
        hashmap_88.put(new Student("张三", 23), "北京");
        hashmap_88.put(new Student("李四", 24), "南京");
        HashMap<Student, String> hashmap_99 = new HashMap<Student, String>();
        hashmap_99.put(new Student("王五", 23), "上海");
        hashmap_99.put(new Student("赵六", 24), "深圳");
        HashMap<HashMap<Student, String>, String> hm = new HashMap<HashMap<Student, String>, String>();
        hm.put(hashmap_88, "第88期基础班");
        hm.put(hashmap_99, "第99期基础班");
        
        System.out.println("遍历方式一");
        Set<HashMap<Student, String>> ks = hm.keySet();
        Iterator<HashMap<Student, String>> it1 = ks.iterator();
        while(it1.hasNext()) {
            HashMap<Student,String> next_stu_value = it1.next();
            Set<Student> stu_set = next_stu_value.keySet();
            Iterator<Student> stu_it = stu_set.iterator();
            System.out.println(hm.get(next_stu_value)+"有以下学生");
            while(stu_it.hasNext()) {
                Student student = stu_it.next();
                System.out.println("个人信息"+student);
            }
        }
        
        System.out.println("遍历方式二");
        for (HashMap<Student, String> hashMap : hm.keySet()) {
            System.out.println(hm.get(hashMap)+"有以下学生");
            for (Student stu : hashMap.keySet()) {
                System.out.println("个人信息"+stu);
            }
        }
        System.out.println("遍历方式三");
        Set<HashMap<Student,String>> x=hm.keySet();
        for(Iterator<HashMap<Student,String>> it= x.iterator();it.hasNext();) {
             HashMap<Student, String> stu_map_value = it.next();
             System.out.println(hm.get(stu_map_value)+"有以下学生");
            for( Iterator<Student> it2 = stu_map_value.keySet().iterator();it2.hasNext();) {
                Student student = it2.next();
                System.out.println("个人信息"+student);
            }
        }
        System.out.println("遍历方式四");
        Set<Entry<HashMap<Student,String>,String>> entrySet = hm.entrySet();
        Iterator<Entry<HashMap<Student, String>, String>> itentry = entrySet.iterator();
        while(itentry.hasNext()) {
            Entry<HashMap<Student, String>, String> entry = itentry.next();
            HashMap<Student,String> map = entry.getKey();
            System.out.println(entry.getValue()+"有以下学生");
            Iterator<Entry<Student, String>> iterator = map.entrySet().iterator();
             while(iterator.hasNext()) {
                 Entry<Student, String> next = iterator.next();
                    System.out.println("个人信息"+next.getKey()+" "+next.getValue());
             }
        }
        System.out.println("遍历方式五");
        for (Map.Entry<HashMap<Student, String>, String> entry : hm.entrySet()) {
            System.out.println(entry.getValue()+"有以下学生");
            for (Map.Entry<Student,String> stu : entry.getKey().entrySet()) {
                System.out.println("个人信息"+stu.getKey()+" "+stu.getValue());
            }
        }
        System.out.println("遍历方式六");
        hm.forEach((K,V)->{
            System.out.println(V+"有以下学生");
            K.forEach((sub_K,sub_V)->{
                System.out.println("个人信息"+sub_K+" "+sub_V);
            });
        });
        
        Iterator<HashMap<Student, String>> ite2 = hm.keySet().iterator();
        while(ite2.hasNext()) {
            HashMap<Student,String> next = ite2.next();
            Iterator<Entry<Student, String>> iterator = next.entrySet().iterator();
            while(iterator.hasNext()) {
                Entry<Student, String> entry = iterator.next();
                if(entry.getValue().equals("深圳")) {
                    iterator.remove();
                }
            }
        }
        System.out.println("-=-----------------------");
        hm.forEach((K,V)->{
            System.out.println(V+"有以下学生");
            K.forEach((sub_K,sub_V)->{
                System.out.println("个人信息"+sub_K+" "+sub_V);
            });
        });
        
        
    }
}