Java 8 将二维数组转换为具有键重复检查的映射

Question

在 java 8 中如何使用 stream() 将 2D array 转换为地图。如果键值已经存在，它也应该更新值。

String[][] array=new String[][]{{"a","b"},{"a","c"},{"b","d"}};
HashMap<String,String> map=new HashMap<String,String>();
for(String[] arr:array){
   map.put(arr[0],arr[1]);
}

我试过了

map=Arrays.stream(array).collect(Collectors.toMap(x->x[0],x->x[1]));

错误

Error:(38, 45) java: incompatible types: inference variable R has incompatible bounds equality constraints: java.util.Map upper bounds: java.util.HashMap,java.lang.Object

Answer 1

添加合并重复键的运算符：

String[][] array = new String[][]{{"a", "b"}, {"a", "c"}, {"b", "d"}};

Map<String, String> m = Arrays.stream(array)
                              .collect(Collectors.toMap(  kv -> kv[0],
                                                          kv -> kv[1],
                                                          (oldV, newV) -> newV)
                                                       ));

_{有一天格式化这些单行将成为一个问题..}

Java 8 将二维数组转换为具有键重复检查的映射

Java 8 Convert 2D array into Map with key duplication check

java

java-8

java-stream