print map java

1map.forEach((key, value) -> System.out.println(key + ":" + value));

1// 1. for-each with Entry
2Map<Integer, Integer> map = new HashMap<Integer, Integer>();
3for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
4    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
5}
6
7
8// 2. for-each with key or value each (faster)
9Map<Integer, Integer> map = new HashMap<Integer, Integer>();
10//iterating over keys only
11for (Integer key : map.keySet()) {
12    System.out.println("Key = " + key);
13}
14 
15//iterating over values only
16for (Integer value : map.values()) {
17    System.out.println("Value = " + value);
18}
19
20
21// 3. Using Iterator
22Map<Integer, Integer> map = new HashMap<Integer, Integer>();
23// With Generic
24Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
25while (entries.hasNext()) {
26    Map.Entry<Integer, Integer> entry = entries.next();
27    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
28}
29
30// No Generic
31Map map = new HashMap();
32Iterator entries = map.entrySet().iterator();
33while (entries.hasNext()) {
34    Map.Entry entry = (Map.Entry) entries.next();
35    Integer key = (Integer)entry.getKey();
36    Integer value = (Integer)entry.getValue();
37    System.out.println("Key = " + key + ", Value = " + value);
38}
39

1import java.util.HashMap;
2import java.util.Iterator;
3import java.util.Map;
4import java.util.stream.Stream;
5 
6class MapUtil
7{
8    // Program to print all keys present in the Map using keySet() in Java
9    public static void main (String[] args)
10    {
11        Map<Integer, String> map = new HashMap<>();
12        map.put(1, "One");
13        map.put(2, "Two");
14 
15        // 1. using Iterator
16        Iterator<Integer> itr = map.keySet().iterator();
17        while (itr.hasNext()) {
18            System.out.println(itr.next());
19        }
20 
21        // 2. For-each Loop
22        for (Integer key : map.keySet()) {
23            System.out.println(key);
24        }
25 
26        // 3. Java 8 - Collection.iterator() + Iterator.forEachRemaining()
27        map.keySet().iterator()
28                .forEachRemaining(System.out::println);
29 
30        // 4. Java 8 - Collection.stream() + Stream.forEach()
31        map.keySet().stream()
32                .forEach(System.out::println);
33 
34        // Java 8 - Stream.of() + Collection.toArray() + Stream.forEach()
35        Stream.of(map.keySet().toArray())
36                .forEach(System.out::println);
37 
38        // 5. Convert to String
39        System.out.println(map.keySet().toString());
40 
41        // Java 8
42        Stream.of(map.keySet().toString())
43                .forEach(System.out::println);
44    }
45}
46

1// Java 8 - Collection.iterator() + Iterator.forEachRemaining()
2        map.keySet().iterator()
3                .forEachRemaining(System.out::println);

1Map<String, Integer> map = new HashMap<>();
2map.put("a", 1);
3map.put("b", 2);
4System.out.println(Arrays.asList(map)); // method 1
5System.out.println(Collections.singletonList(map)); // method 2
6