1.键找值 keySet()
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public class MapDemo2 {public static void main(String[] args) {//Map集合中的第一种遍历方式//键找值Map<String, String> m = new HashMap<>();m.put("神原秋人", "栗山未来");m.put("夏目贵志", "斑");m.put("平泽唯", "中野梓");//通过键找值//获取所有的键，存到单列集合中Set<String> keys = m.keySet();//遍历单列集合，得到每一个键//增强forfor (String key : keys) {//利用m集合中的键获取对应的值String value = m.get(key);System.out.println(key + " = " + value);}System.out.println("---------------------------------------");//迭代器Iterator<String> it = keys.iterator();while (it.hasNext()) {String key = it.next();String value = m.get(key);System.out.println(key + " = " + value);}System.out.println("---------------------------------------");//lambda表达式keys.forEach(key -> {String value = m.get(key);System.out.println(key + " = " + value);});}
}
2.通过键值对对象遍历
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public class MapDemo3 {public static void main(String[] args) {//第二种遍历方式Map<String, String> map = new HashMap<>();map.put("神原秋人", "栗山未来");map.put("夏目贵志", "斑");map.put("平泽唯", "中野梓");//通过一个方法获取所有键值对对象，返回一个Set集合Set<Map.Entry<String, String>> entries = map.entrySet();//遍历entries集合，得到每一个键值对对象//利用entry调用getKey、getValue获取键和值//增强forfor (Map.Entry<String, String> entry : entries) {String key = entry.getKey();String value = entry.getValue();System.out.println(key + " = " + value);}System.out.println("---------------------------------------");//迭代器Iterator<Map.Entry<String, String>> it = entries.iterator();while (it.hasNext()) {Map.Entry<String, String> entry = it.next();String key = entry.getKey();String value = entry.getValue();System.out.println(key + " = " + value);}System.out.println("---------------------------------------");//lambda表达式entries.forEach(entry -> {String key = entry.getKey();String value = entry.getValue();System.out.println(key + " = " + value);});}
}
3.Lambda表达式遍历
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public class MapDemo4 {public static void main(String[] args) {//第三种遍历方式Map<String, String> map = new HashMap<>();map.put("神原秋人", "栗山未来");map.put("夏目贵志", "斑");map.put("平泽唯", "中野梓");//利用lambda表达式进行遍历//底层：//forEach其实就是利用第二种方式进行遍历，依次得到每一个键和值//再调用accept方法map.forEach(new BiConsumer<String, String>() {@Overridepublic void accept(String key, String value) {System.out.println(key + " = " + value);}});//简化//map.forEach((key, value) -> System.out.println(key + " = " + value));}
}