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| 1 | +# 初始化静态map # |
| 2 | + |
| 3 | +## 问题 ## |
| 4 | + |
| 5 | +怎么在Java中初始化一个静态的map |
| 6 | + |
| 7 | +**方法一**:静态初始化器 |
| 8 | + |
| 9 | +**方法二**:实例初始化(匿名子类) |
| 10 | + |
| 11 | +下面是描述上面两种方法的例子 |
| 12 | + |
| 13 | + import java.util.HashMap; |
| 14 | + import java.util.Map; |
| 15 | + public class Test{ |
| 16 | + private static final Map<Integer, String> myMap = new HashMap<Integer, String>(); |
| 17 | + static { |
| 18 | + myMap.put(1, "one"); |
| 19 | + myMap.put(2, "two"); |
| 20 | + } |
| 21 | + |
| 22 | + private static final Map<Integer, String> myMap2 = new HashMap<Integer, String>(){ |
| 23 | + { |
| 24 | + put(1, "one"); |
| 25 | + put(2, "two"); |
| 26 | + } |
| 27 | + }; |
| 28 | + } |
| 29 | + |
| 30 | +## 答案 ## |
| 31 | + |
| 32 | +### 答案1 ### |
| 33 | + |
| 34 | +匿名子类初始化器是java的语法糖,我搞不明白为什么匿名类来初始化,而且如果create的类是final的话,它将不起作用 |
| 35 | + |
| 36 | +我创建固定大小图的时候使用static初始化器 |
| 37 | + |
| 38 | + public class Test{ |
| 39 | + private static final Map<Integer, String> myMap; |
| 40 | + static{ |
| 41 | + Map<Integer, String> aMap = ...; |
| 42 | + aMap.put(1,"one"); |
| 43 | + aMap.put(2,"two"); |
| 44 | + myMap = Collections.unmodifiableMap(aMap); |
| 45 | + } |
| 46 | + } |
| 47 | + |
| 48 | + |
| 49 | +### 答案2 ### |
| 50 | + |
| 51 | +我喜欢用Guava(是 Collection 框架的增强和扩张)的方法初始化一个静态的,不可改变的map |
| 52 | + |
| 53 | + static fianl Map<Integer, String> myMap = ImmutablMap.of( |
| 54 | + 1,"one", |
| 55 | + 2, "two" |
| 56 | + ) |
| 57 | +· |
| 58 | +当你的图entry的个数超过5个时候你就不能使用`ImmutableMap.of`可以试试`ImmutableMap.bulider()` |
| 59 | + |
| 60 | + static fianl Map<Integer, String> myMap = ImmutableMap.<Integer, String>builder() |
| 61 | + { |
| 62 | + .put(1, "one") |
| 63 | + .put(2, "two") |
| 64 | + |
| 65 | + .put(15, "fifteen") |
| 66 | + .build(); |
| 67 | + } |
| 68 | + |
| 69 | + |
| 70 | +# 原文链接 # |
| 71 | + |
| 72 | +http://stackoverflow.com/questions/507602/how-can-i-initialize-a-static-map |
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