Question

我试图将静态数据插入Java中的 HashMap ，如下所示：

HashMap<String,String[]> instruments = new HashMap<String, String[]>();
instruments.put("EURUSD", {"4001","EURUSD","10000","0.00001","0.1","USD"});

但是编译器不喜欢它。我发现将数据插入HashMap的唯一方法是分别声明字符串数组，然后将其放入HashMap中，就像这样

String[] instruDetails = {"4001","EURUSD","10000","0.00001","0.1","USD"};
instruments.put("EURUSD", instruDetails);

但它表达力不强，难以维持

所以我的问题是，有没有办法在一个步骤/行中执行put()操作和字符串数组声明？

Answer 1

这样做：

instruments.put("EURUSD", new String[]{"4001","EURUSD","10000","0.00001","0.1","USD"});

Answer 2

要在一个句子中全部使用，请使用双括号初始化： -

 HashMap<String,String[]> instruments = new HashMap<String, String[]>() {
     {
      put("EURUSD", new String[]{"4001","EURUSD","10000","0.00001","0.1","USD"});
      put("EUR", new String[]{"4001","EURUSD","10000","0.00001","0.1","USD"});
     }
 };

Answer 3

我认为你已经有了可行的方法。但原因是

instruments.put("EURUSD", {"4001","EURUSD","10000","0.00001","0.1","USD"});

不起作用是因为{"4001","EURUSD","10000","0.00001","0.1","USD"}。 {}是Java数组中用于初始化的语法糖或快捷方式。它带有一个约束，它总是必须与数组声明语句一起使用，否则它是语法错误。

数组声明语句，如

String[] array = {"1", "2"};

这样Java知道它需要为你创建的数组实际上是String类型的元素。

如果您违反以上声明如下

String[] array;
array = {"1", "2"};

它无法编译。

使用new String[]{"4001","EURUSD","10000","0.00001","0.1","USD"}，编译器知道它必须实例化一个新数组，其元素类型为String（new String[]）并使用您提供的值初始化新实例化的数组（ {"4001","EURUSD","10000","0.00001","0.1","USD"}）。

只需一步即可在HashMap中声明和放置String数组

3 个答案: