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基于 React + Redux/ 搞定复杂项目状态管理内附资料
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1.JDK 8 之前的遍历
JDK 8 之前主要使用 EntrySet 和 KeySet 进行遍历,具体实现代码如下。
1.1 EntrySet 遍历
EntrySet 是早期 HashMap 遍历的主要方法,其实现代码如下:
public static void main(String[] args) { // 创建并赋值 hashmap HashMap<String, String> map = new HashMap() {{ put("Java", " Java Value."); put("MySQL", " MySQL Value."); put("Redis", " Redis Value."); }}; // 循环遍历 for (Map.Entry<String, String> entry : map.entrySet()) { System.out.println(entry.getKey() + ":" + entry.getValue()); } }
1.2 KeySet 遍历
KeySet 的遍历方式是循环 Key 内容,再通过 map.get(key) 获取 Value 的值,具体实现如下:
public static void main(String[] args) { // 创建并赋值 hashmap HashMap<String, String> map = new HashMap() {{ put("Java", " Java Value."); put("MySQL", " MySQL Value."); put("Redis", " Redis Value."); }}; // 循环遍历 for (String key : map.keySet()) { System.out.println(key + ":" + map.get(key)); } }
1.3 EntrySet 迭代器遍历
EntrySet 和 KeySet 除了以上直接循环外,我们还可以使用它们的迭代器进行循环,如 EntrySet 的迭代器实现代码如下:
public static void main(String[] args) { // 创建并赋值 hashmap HashMap<String, String> map = new HashMap() {{ put("Java", " Java Value."); put("MySQL", " MySQL Value."); put("Redis", " Redis Value."); }}; // 循环遍历 Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry<String, String> entry = iterator.next(); System.out.println(entry.getKey() + ":" + entry.getValue()); } }
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