如何在Java 7中使用收集文字？ [英] How do I use collection literals in Java 7?

问题描述

我试过下面这行：

Map<Character, Color> map={new Character('r'):Color.red,new Character('b'):Color.black};

< ';'expected 。

我将Source / Binary格式设置为JDK 7，平台设置为JDK 1.7，还有其他需要做的事吗？

I've set the Source/Binary format as 'JDK 7'and the platform to 'JDK 1.7', is there anything else I need to do?

推荐答案

Java 7不支持收集文字。 他们计划在Java 8。他们没有使它甚至进入Java 8，如这个问题讨论： Project Coin的集合增强功能将在JDK8中？

Java 7 does not support collection literals. They are planned for Java 8. They didn't make it even into Java 8 as discussed in this question: Are Project Coin's collection enhancements going to be in JDK8?

如果您只需要不可变的集合，请使用Google的 Guava 库。 ImmutableList ， ImmutableSet 和 ImmutableMap 有几个重载的工厂方法，甚至是创建集合的构建器：

You can use Google's Guava library if you need only immutable collections. ImmutableList, ImmutableSet and ImmutableMap have several overloaded factory methods or even builders that make creating collections easy:

List<Integer> list = ImmutableList.of(1, 1, 2, 3, 5, 8, 13, 21);
Set<String> set = ImmutableSet.of("foo", "bar", "baz", "batman");
Map<Integer, String> map = ImmutableMap.of(1, "one", 2, "two", 3, "three");

EDIT

Java 9可能会添加类似于Guava的收集工厂方法：

Java 9 will probably add collection factory methods similar to those of Guava:

List.of(a, b, c);
Set.of(d, e, f, g);
Map.of(k1, v1, k2, v2)

Map.ofEntries(
    entry(k1, v1),
    entry(k2, v2),
    entry(k3, v3),
    // ...
    entry(kn, vn)
);

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