新的ConcurrentHashMap的新ConcurrentHashMap [英] new ConcurrentHashMap of new ConcurrentHashMap

问题描述

我正在尝试使用

初始化ConcurrentHashMap的ConcurrentHashMap

private final ConcurrentHashMap<
    String, 
    ConcurrentHashMap<String, Double>
> myMulitiConcurrentHashMap = new ConcurrentHashMap<
    String, 
    new ConcurrentHashMap<String, Double>()
>();

但是javac给出

HashMapper.java:132: error: illegal start of type
    new ConcurrentHashMap<String, Double>()
    ^
HashMapper.java:132: error: '(' or '[' expected
    new ConcurrentHashMap<String, Double>()
        ^
HashMapper.java:132: error: ';' expected
    new ConcurrentHashMap<String, Double>()

指向第二个new.

如何正确地new初始化new?

推荐答案

顺便说一句，Java 7现在有了更简洁的语法(钻石"):

By the way, Java 7 has a more concise syntax now (the "diamond"):

private final 
   ConcurrentHashMap<String, ConcurrentHashMap<String, Double>>
      myMulitiConcurrentHashMap =
         new ConcurrentHashMap<>();

您也应该能够使用左侧的界面:

You should be able to use interfaces on the left hand side, too:

private final 
   ConcurrentMap<String, ConcurrentMap<String, Double>>
      myMulitiConcurrentHashMap =
         new ConcurrentHashMap<>();

这篇关于新的ConcurrentHashMap的新ConcurrentHashMap的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！