如何通過LinkedHashMap <String，ArrayList <String>>創建一個循環？

Question

請幫我通過LinkedHashMap<String,ArrayList<String>> h創建一個循環：

if (h.get("key1").size() == 0) 
    System.out.println("There is no errors in key1."); 
else 
    System.out.println("ERROR: there are unexpected errors in key1."); 

if (h.get("key2").size() == 0) 
    System.out.println("There is no errors in key2."); 
else 
    System.out.println("ERROR: there are unexpected errors in key2."); 

if (h.get("key3").size() == 0) 
    System.out.println("There is no errors in key3."); 
else 
    System.out.println("ERROR: there are unexpected errors in key3."); 

if (h.get("key4").size() == 0) 
    System.out.println("There is no errors in key4.\n"); 
else 
    System.out.println("ERROR: there are unexpected errors in key4.\n"); 

Answer 1

喜歡這個？

for (String key : h.keySet()) 
{ 
    System.out.println("Key: " + key); 
    for(String str : h.get(key)) 
    { 
     System.out.println("\t" +str); 
    } 
} 

編輯：

for (String key : h.keySet()) 
{ 
    if(h.get(key).size() == 0) 
    { 
     System.out.println("There is no errors in " + key) ; 
    } 
    else 
    { 
     System.out.println("ERROR: there are unexpected errors in " + key); 
    } 
} 

Answer 2

試試這個代碼：

Map<String, ArrayList<String>> a = new LinkedHashMap<String, ArrayList<String>>(); 
Iterator<Entry<String,ArrayList<String>>> itr = a.entrySet().iterator(); 
while (itr.hasNext()) { 
    Entry<String,ArrayList<String>> entry = itr.next(); 
    String key = entry.getKey(); 
    System.out.println("key: " + key); 
    List<String> list = entry.getValue(); 
    System.out.println("value: " + list); 
} 

Answer 3

在Java8另一種方法是用foreach()方法

Map<String, List<String>> test1 = new LinkedHashMap<String, List<String>>(); 
test1.forEach((key,value) -> { 
    System.out.println(key + " -> " + value); 
});