java遍历Map的四种方法
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public static void main(String[] args) {
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Map<String, String> map = new HashMap<String, String>();
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map.put("1", "value1");
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map.put("2", "value2");
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map.put("3", "value3");
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//第一种：普遍使用。二次取值
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System.out.println("通过Map.keySet遍历key和value：");
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for (String key : map.keySet()) {
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System.out.println("key= "+ key + " and value= " + map.get(key));
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}
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//另外一种
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System.out.println("通过Map.entrySet使用iterator遍历key和value：");
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Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
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while (it.hasNext()) {
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Map.Entry<String, String> entry = it.next();
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System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
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}
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//第三种：推荐，尤其是容量大时
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System.out.println("通过Map.entrySet遍历key和value");
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for (Map.Entry<String, String> entry : map.entrySet()) {
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System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
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}
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//第四种
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System.out.println("通过Map.values()遍历全部的value。但不能遍历key");
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for (String v : map.values()) {
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System.out.println("value= " + v);
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}
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}
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