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Java how to use forEach () method to traverse List and Map, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can get something.

List / / List

List list = new ArrayList (6)

List.add ("1")

List.add ("2")

For (Iterator iterator = list.iterator (); iterator.hasNext ();) {

String item = iterator.next ()

System.out.println (item)

If (conditions for deleting elements) {

Iterator.remove ()

}

}

Map

Specification:

Use entrySet to traverse the Map class collection KV instead of keySet.

Note: keySet is actually traversed twice, once converted to an Iterator object, and the other is to extract the value corresponding to key from hashMap. EntrySet only traverses once and then puts both key and value into entry, which is more efficient. If it is JDK8, use the Map.forEach method.

Positive example: values () returns a V-value collection, which is a list collection object; keySet () returns a K-value collection, which is a Set set object; and entrySet () returns a K-value combination collection.

/ / Map uses entrySet

HashMap map = new HashMap (6)

Map.put ("a", 1)

Map.put ("b", 2)

For (Map.Entry entry: map.entrySet ()) {

System.out.println ("key:" + entry.getKey () + "\ tvalue:" + entry.getValue ())

}

Use forEach () + Lambda expression / / List after Java 8

List list = new ArrayList (6)

List.add ("1")

List.add ("2")

List.forEach (v-> System.out.println (v))

/ / Map

HashMap map = new HashMap (6)

Map.put ("a", 1)

Map.put ("b", 2)

Map.forEach ((KBI v)-> {

System.out.println ("key:" + k + "\ tvalue:" + v)

});

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