Check out example codes for "java 8 map foreach". It will help you in understanding the concepts better.

Code Example 1

Optional<List> o = id1.entrySet()
                      .stream()
                      .filter( e -> e.getKey() == 1)
                      .map(Map.Entry::getValue)
                      .findFirst();

Code Example 2

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);

items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));

items.forEach((k,v)->{
	System.out.println("Item : " + k + " Count : " + v);
	if("E".equals(k)){
		System.out.println("Hello E");
	}
});

Code Example 3

public void iterateUsingLambda(Map<String, Integer> map) {
    map.forEach((k, v) -> System.out.println((k + ":" + v)));
}

Code Example 4

public void iterateUsingIteratorAndEntry(Map<String, Integer> map) {
    Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
    while (iterator.hasNext()) {
        Map.Entry<String, Integer> entry = iterator.next();
        System.out.println(entry.getKey() + ":" + entry.getValue());
    }
}

Code Example 5

public void iterateUsingEntrySet(Map<String, Integer> map) {
    for (Map.Entry<String, Integer> entry : map.entrySet()) {
        System.out.println(entry.getKey() + ":" + entry.getValue());
    }
}

Code Example 6

public void iterateUsingStreamAPI(Map<String, Integer> map) {
    map.entrySet().stream()
      // ...
      .forEach(e -> System.out.println(e.getKey() + ":" + e.getValue()));
}

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