java - 如何在字符串数组中查找重复的字符串

Question

我有以下代码，我只想检索那些重复的值，但找不到正确的结果。我不知道我错在哪里。

public class TestDummy {
    public static void main(String args[]){
       String arr[] ={"lady", "bird", "is","bird","lady","cook"};
       int len = arr.length;
       System.out.println("Size "+len);
       for(int i=0 ; i<=len;i++){
           for(int j=1 ; j< len-1;j++){
            if(arr[i]==arr[j]){
              System.out.println("Duplicate "+arr[i]);
          } 
       }  
           }
    }


}

Answer 1

    String arr[] ={"lady", "bird", "is","bird","lady","cook"};
    Map<String, Integer> map = new HashMap<>();
    for(String str: arr) {
        if(map.containsKey(str)) {
            map.put(str, map.get(str)+1);
        } else{
            map.put(str, 1);
        }
    }
    for(String str: map.keySet()) {
        if(map.get(str) > 1) {
            System.out.println("Duplicate: "+ str+" count:"+map.get(str));
        }
    }

输出:

Duplicate: bird count:2
Duplicate: lady count:2