Java中遍历Map的n种方法

forEach

public static void fashion(Map<String, String> map) {
    map.forEach((key, value) -> System.out.println("key = " + key + ", value = " + value));
}

keySet + forEach

public static void fashion(Map<String, String> map) {
    Set<String> keySet = map.keySet();
    keySet.forEach(key -> {
        System.out.println("key = " + key + ", value = " + map.get(key));
    });
}

keySet + for 循环

public static void fashion(Map<String, String> map) {
    Set<String> keySet = map.keySet();
    for (String key : keySet) {
        System.out.println("key = " + key + ", value = " + map.get(key));
    }
}

keySet + iterator

public static void fashion(Map<String, String> map) {
    Set<String> keySet = map.keySet();
    Iterator<String> iterator = keySet.iterator();
    while (iterator.hasNext()) {
        String next = iterator.next();
        System.out.println("key = " + next + ", value = " + map.get(next));
    }
}

keySet + stream 流

public static void fashion(Map<String, String> map) {
    map.keySet().stream().forEach(key -> {
        System.out.println("key = " + key + ", value = " + map.get(key));
    });
}

entrySet + forEach

public static void fashion5(Map<String, String> map) {
    Set<Map.Entry<String, String>> entrySet = map.entrySet();
    entrySet.forEach(entry -> {
        System.out.println("key = " + entry.getKey() + ", value = " + entry.getValue());
    });
}

entrySet + for 循环

public static void fashion4(Map<String, String> map) {
    Set<Map.Entry<String, String>> entrySet = map.entrySet();
    for (Map.Entry<String, String> entry : entrySet) {
        System.out.println("key = " + entry.getKey() + ", value = " + entry.getValue());
    }
}

entrySet + iterator

public static void fashion5(Map<String, String> map) {
    Set<Map.Entry<String, String>> entrySet = map.entrySet();
    Iterator<Map.Entry<String, String>> iterator = entrySet.iterator();
    while (iterator.hasNext()) {
        Map.Entry<String, String> next = iterator.next();
        System.out.println("key = " + next.getKey() + ", value = " + next.getValue());
    }
}

entrySet + stream 流

public static void fashion7(Map<String, String> map) {
    map.entrySet().stream().forEach(entry -> {
        System.out.println("key = " + entry.getKey() + ", value = " + entry.getValue());
    });
}

Map#values 只能拿到所有 value

public static void fashion6(Map<String, String> map) {
    Collection<String> values = map.values();
    for (String value : values) {
        System.out.println("value = " + value);
    }
}