我如何在一个对象中预加载一个hashmap（没有put方法）？ [英] how do i preload a hashmap in an object(without put method)?

问题描述

我有一个类，它有几个数据结构，其中是一个hashmap。但是我希望hashmap有默认值，所以我需要预加载它。我怎么做，因为我不能在对象内使用put方法？

  class Profile 
 {
 HashMap closedAges = new HashMap（）; 
 closedAges.put（19）; 
} 
  

我用这个修改了它，但是我不得不在对象中使用一个方法。

  class Profile 
 {
 HashMap closedAges = loadAges（）; 
 HashMap loadAges（）
 {
 HashMap closedAges = new HashMap（）; 
 
 String [] ages = {19，46，54，56，83}; 
 for（String age：ages）
 {
 closedAges.put（age，false）; 
} 
 return closedAges; 
} 
} 
  

解决方案

你可以这样做：

  Map< String，String> map = new HashMap< String，String>（）{{
 put（1，one）; 
 put（2，two）; 
 put（3，three）; 
}}; 
  

这个java成语被称为 双重括号初始化 。：

创建一个新的AnonymousInnerClass，第二个声明一个实例初始化程序块，当匿名内部类被实例化时运行。

I have a class and it has a couple data structures in it among which is a hashmap. But I want the hashmap to have default values so I need to preload it. How do I do this since I can't use put method inside the object?

class Profile
{
    HashMap closedAges = new HashMap();
    closedAges.put("19");
}

I fixed it with this but I had to use a method within the object.

class Profile
{   
    HashMap closedAges = loadAges();
    HashMap loadAges()
    {
        HashMap closedAges = new HashMap();

        String[] ages = {"19", "46", "54", "56", "83"};
        for (String age : ages)
        {
            closedAges.put(age, false);
        }
        return closedAges;
    }
}

解决方案

You could do this:

Map<String, String> map = new HashMap<String, String>() {{
   put("1", "one");
   put("2", "two");
   put("3", "three");
}};

This java idiom is called double brace initialization.:

The first brace creates a new AnonymousInnerClass, the second declares an instance initializer block that is run when the anonymous inner class is instantiated.

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