如何在java中定義KeyPairValue中的值

Question

我確實對我的應用程序有很多角色。

private static HashMap<String, String> doctorcredentials = new HashMap<String, String>("doctor","Test1234!"); 

它引發我錯誤，以消除參數。每次我只需要添加此憑據。無法直接定義？

Answer 1

由於documentation沒有構造可以從收集比現有的地圖等

public HashMap(Map<? extends K,? extends V> m) 

以滿足新的HashMap的正確方法是增加對逐個創建新實例後創建HashMap

private static HashMap<String, String> doctorcredentials = new HashMap<String, String>(); 
    doctorcredentials.put("doctor","Test1234!"); 
    //etc... 

---

無論如何，你可以創建一個工廠類，將爲你創建HashMaps - 類似

//You need to add casting exception handling, no argument situation etc... 
    public class HashMapFactory<T, V> { 
     public HashMap<T, V> create(Object... arg) { 
      HashMap<T, V> map = new HashMap<T, V>(); 

      for(int i = 1; i < arg.length; i+=2) { 
       map.put((T)arg[i-1], (V)arg[i]); 
      } 

      return map; 
     } 
    } 

然後你可以使用這個喜歡

HashMapFactory<String, String> factory = new HashMapFactory<String, String>(); 

    HashMap<String, String> map = factory.create("one", "two", "three", "four", "five", "six"); 
    System.out.println(map.get("five")); 

Answer 2

HashMap中沒有一個構造函數來支持你指定的參數。請參考documentation

爲了把值HashMap中使用的情況下

HashMap<String, String> hm = new HashMap<String, String>(); 

hm.put("first", "FIRST INSERTED"); 
hm.put("second", "SECOND INSERTED"); 
hm.put("third","THIRD INSERTED"); 

Answer 3

按照規定，我認爲要做到這一點：

private static HashMap<String, String> doctorcredentials = new HashMap<String, String>(); 
doctorcredentials.put("doctor","Test1234!"); 

Answer 4

，你可以簡單地聲明自己的地圖是這樣的：

private static HashMap<String, String> doctorcredentials = new HashMap<String, String>() { 
    { 
     put("doctor","Test1234!"); 
    } 
};