2018년 3월 23일 금요일

[Java] Map Iteration Examples



There are five cases for map iteration in the example.

main function for test:
1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
public static void main(String[] args) {
        Map<String,String> map = new TreeMap<>();
        map.put( "one", "first");
        map.put( "two", "second");
        map.put( "three", "third");
        
        printUsingIterator(map);
        printUsingKeySet(map);
        printUsingEntrySet(map);
        printUsingForEach(map);
        printUsingStream(map);
    }



1.  Map Iteration using keySet + Iterator

1
2
3
4
5
6
7
static  void printUsingIterator(Map<String,String> map) {
        Iterator<String> keys = map.keySet().iterator();
        while( keys.hasNext() ){
            String key = keys.next();
            System.out.println( String.format("(%s -> %s)", key, map.get(key)) );
        }
    }


2.  Map Iteration using keySet

1
2
3
4
5
static void printUsingKeySet(Map<String,String> map) {
        for( String key : map.keySet() ) {
            System.out.println( String.format("(%s -> %s)", key, map.get(key)) );
        }
    }


3.  Map Iteration using entrySet

1
2
3
4
5
static void printUsingEntrySet(Map<String,String> map) {
        for( Map.Entry<String, String> m : map.entrySet() ){
            System.out.println( String.format("(%s -> %s)", m.getKey(), m.getValue()) );
        }
    }


4.  Map Iteration using forEach

1
2
3
static void printUsingForEach(Map<String,String> map) {
        map.forEach( (k,v) -> System.out.println(String.format("(%s -> %s)", k, v )) );
    }


5.  Map Iteration using stream + forEach

1
2
3
4
static void printUsingStream(Map<String,String> map) {
        map.entrySet().stream()
            .forEach( m -> System.out.println(String.format("(%s -> %s)",  m.getKey(), m.getValue())));
    }



Full Source:

1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
package bloggerpostsnippetjava;

import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

public class Inerations {
    
   static  void printUsingIterator(Map<String,String> map) {
        Iterator<String> keys = map.keySet().iterator();
        while( keys.hasNext() ){
            String key = keys.next();
            System.out.println( String.format("(%s -> %s)", key, map.get(key)) );
        }
    }
    
    static void printUsingKeySet(Map<String,String> map) {
        for( String key : map.keySet() ) {
            System.out.println( String.format("(%s -> %s)", key, map.get(key)) );
        }
    }
    
    static void printUsingEntrySet(Map<String,String> map) {
        for( Map.Entry<String, String> m : map.entrySet() ){
            System.out.println( String.format("(%s -> %s)", m.getKey(), m.getValue()) );
        }
    }

    static void printUsingForEach(Map<String,String> map) {
        map.forEach( (k,v) -> System.out.println(String.format("(%s -> %s)", k, v )) );
    }

    static void printUsingStream(Map<String,String> map) {
        map.entrySet().stream()
            .forEach( m -> System.out.println(String.format("(%s -> %s)",  m.getKey(), m.getValue())));
    }
        
    public static void main(String[] args) {
        Map<String,String> map = new TreeMap<>();
        map.put( "one", "first");
        map.put( "two", "second");
        map.put( "three", "third");
        
        printUsingIterator(map);
        printUsingKeySet(map);
        printUsingEntrySet(map);
        printUsingForEach(map);
        printUsingStream(map);
    }
}

Result:
(one -> first)
(three -> third)
(two -> second)
     ...



on
라벨:

댓글 없음:

댓글 쓰기

피드 구독하기: 댓글 (Atom)