Java根据键(Key)输出值(value)应该怎么办？小白刚接触Map

Question

如题所述

Answer 1

ava中遍历MAP的几种方法 

Java代码
Map<String,String> map=new HashMap<String,String>();    

map.put("username", "qq");    

map.put("passWord", "123");    

map.put("userID", "1");    

map.put("email", "[email protected]");   

Map<String,String> map=new HashMap<String,String>();
map.put("username", "qq");
map.put("passWord", "123");
map.put("userID", "1");
map.put("email", "[email protected]");
第一种用for循环 

Java代码

for(Map.Entry<String, String> entry:map.entrySet()){    

     System.out.println(entry.getKey()+"--->"+entry.getValue());    

}   

for(Map.Entry<String, String> entry:map.entrySet()){
          System.out.println(entry.getKey()+"--->"+entry.getValue());
 }

第二种用迭代 

Java代码

Set set = map.entrySet();         

Iterator i = set.iterator();         

while(i.hasNext()){      

     Map.Entry<String, String> entry1=(Map.Entry<String, String>)i.next();    

     System.out.println(entry1.getKey()+"=="+entry1.getValue());    

}   

Set set = map.entrySet();     

Iterator i = set.iterator();     

while(i.hasNext()){  

    Map.Entry<String, String> entry1=(Map.Entry<String, String>)i.next();
    System.out.println(entry1.getKey()+"=="+entry1.getValue());
}
用keySet()迭代 

Java代码

Iterator it=map.keySet().iterator();    

while(it.hasNext()){    

     String key;    

     String value;    

     key=it.next().toString();    

     value=map.get(key);    

     System.out.println(key+"--"+value);    

}   

Iterator it=map.keySet().iterator();
while(it.hasNext()){
    String key;
    String value;
    key=it.next().toString();
    value=map.get(key);
    System.out.println(key+"--"+value);
}

用entrySet()迭代 

Java代码

Iterator it=map.entrySet().iterator();           

System.out.println( map.entrySet().size());    

String key;           

String value;    

while(it.hasNext()){    

        Map.Entry entry = (Map.Entry)it.next();           

        key=entry.getKey().toString();           

        value=entry.getValue().toString();           

        System.out.println(key+"===="+value);                     

}

Answer 2

Map<String,String> maps = new HashMap<String,String>();
//获取key的集合
Set<String> keySet = maps.keySet();
//遍历key集合，获取value
for(String key : keySet) {
String value = maps.get(key);
}

Answer 3

public static void workByEntry(Map<String, Student> map) {
Set<Map.Entry<String, Student>> set = map.entrySet();
for (Iterator<Map.Entry<String, Student>> it = set.iterator(); it.hasNext();) {
Map.Entry<String, Student> entry = (Map.Entry<String, Student>) it.next();
System.out.println(entry.getKey() + "--->" + entry.getValue());
}
}
}

Answer 4

Map.get(Key);

Answer 5

value = map.get(key);