foreach map java

// 1. for-each with Entry
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}


// 2. for-each with key or value each (faster)
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
//iterating over keys only
for (Integer key : map.keySet()) {
    System.out.println("Key = " + key);
}
 
//iterating over values only
for (Integer value : map.values()) {
    System.out.println("Value = " + value);
}


// 3. Using Iterator
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
// With Generic
Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry<Integer, Integer> entry = entries.next();
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

// No Generic
Map map = new HashMap();
Iterator entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry entry = (Map.Entry) entries.next();
    Integer key = (Integer)entry.getKey();
    Integer value = (Integer)entry.getValue();
    System.out.println("Key = " + key + ", Value = " + value);
}

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

// Java program for traversing 
// through a hashmap using for-each loop 
  
import java.util.*; 
  
class GfG { 
    public static void main(String[] args) 
    { 
  
        // Consider the hashmap containing 
        // student name and their marks 
        HashMap<String, Integer> hm =  
                     new HashMap<String, Integer>(); 
  
        // Adding mappings to HashMap 
        hm.put("GeeksforGeeks", 54); 
        hm.put("A computer portal", 80); 
        hm.put("For geeks", 82); 
  
        // Printing the HashMap 
        System.out.println("Created hashmap is" + hm); 
  
        // Loop through the hashmap 
        System.out.println("HashMap after adding bonus marks:"); 
  
        // Using for-each loop 
        for (Map.Entry mapElement : hm.entrySet()) { 
            String key = (String)mapElement.getKey(); 
  
            // Add some bonus marks 
            // to all the students and print it 
            int value = ((int)mapElement.getValue() + 10); 
  
            System.out.println(key + " : " + value); 
        } 
    } 
} 

map.forEach((k, v) -> System.out.printf( " %s : %d \n" , k,v) );

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

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());
    }
}

//traditional way (long)
for(map<string,int>::iterator it=m.begin(); it!=m.end(); ++it)
	if(it->second)cout<<it->first<<" ";
//easy way(short) just works with c++11 or later versions
for(auto &x:m)
	if(x.second)cout<<x.first<<" ";
//condition is just an example of use