java 8 map遍曆方式 (轉)

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public class LambdaMap {    private Map<String, Object> map = new HashMap<>();    @Before    public void initData() {        map.put("key1", "value1");        map.put("key2", "value2");        map.put("key3", "value3");        map.put("key4", 4);        map.put("key5", 5);        map.put("key5", ‘h‘);    }    /**     * 遍曆Map的方式一     * 通過Map.keySet遍曆key和value     */    @Test    public void testErgodicWayOne() {        System.out.println("---------------------Before JAVA8 ------------------------------");        for (String key : map.keySet()) {            System.out.println("map.get(" + key + ") = " + map.get(key));        }        System.out.println("---------------------JAVA8 ------------------------------");        map.keySet().forEach(key -> System.out.println("map.get(" + key + ") = " + map.get(key)));    }    /**     * 遍曆Map第二種     * 通過Map.entrySet使用Iterator遍曆key和value     */    @Test    public void testErgodicWayTwo() {        System.out.println("---------------------Before JAVA8 ------------------------------");        Iterator<Map.Entry<String, Object>> iterator = map.entrySet().iterator();        while (iterator.hasNext()) {            Map.Entry<String, Object> entry = iterator.next();            System.out.println("key:value = " + entry.getKey() + ":" + entry.getValue());        }        System.out.println("---------------------JAVA8 ------------------------------");        map.entrySet().iterator().forEachRemaining(item -> System.out.println("key:value=" + item.getKey() + ":" + item.getValue()));    }    /**     * 遍曆Map第三種     * 通過Map.entrySet遍曆key和value，在大容量時推薦使用     */    @Test    public void testErgodicWayThree() {        System.out.println("---------------------Before JAVA8 ------------------------------");        for (Map.Entry<String, Object> entry : map.entrySet()) {            System.out.println("key:value = " + entry.getKey() + ":" + entry.getValue());        }        System.out.println("---------------------JAVA8 ------------------------------");        map.entrySet().forEach(entry -> System.out.println("key:value = " + entry.getKey() + ":" + entry.getValue()));    }    /**     * 遍曆Map第四種     * 通過Map.values()遍曆所有的value，但不能遍曆key     */    @Test    public void testErgodicWayFour() {        System.out.println("---------------------Before JAVA8 ------------------------------");        for (Object value : map.values()) {            System.out.println("map.value = " + value);        }        System.out.println("---------------------JAVA8 ------------------------------");        map.values().forEach(System.out::println); // 等價於map.values().forEach(value -> System.out.println(value));    }    /**     * 遍曆Map第五種     * 通過k,v遍曆，Java8專屬的     */    @Test    public void testErgodicWayFive() {        System.out.println("---------------------Only JAVA8 ------------------------------");        map.forEach((k, v) -> System.out.println("key:value = " + k + ":" + v));    }}

 

java 8 map遍曆方式 (轉)