What is the unique map traversal mode of JAVA8?
Today, I will talk to you about the unique way of traversing map in JAVA8, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.
Using the map traversal method brought about by JAV8 makes traversal very simple
Public class LambdaMap {private Map 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') } / * ways to traverse Map-* traversing key and value * / @ Test public void testErgodicWayOne () {System.out.println ("- Before JAVA8--") through Map.keySet 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) } / * traversing Map the second * traversing key and value * / @ Test public void testErgodicWayTwo () {System.out.println ("- Before JAVA8--") through Map.entrySet using Iterator; Iterator iterator = map.entrySet () .iterator () While (iterator.hasNext ()) {Map.Entry 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 () } / * traversing Map the third * traverses key and value through Map.entrySet. It is recommended to use * / @ Test public void testErgodicWayThree () {System.out.println ("- Before JAVA8--") for large capacity. For (Map.Entry 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 () } / * * traversing Map the fourth * traverses all value through Map.values (), but cannot traverse 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) / / equivalent to map.values () .forEach (value-> System.out.println (value)) } / * * traversing the fifth kind of Map * through kmenv traversal, Java8's unique * / @ Test public void testErgodicWayFive () {System.out.println ("- Only JAVA8--") Map.forEach ((k, v)-> System.out.println ("key:value =" + k + ":" + v));}}
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