For example, I can loop an ArrayList like this

for (String temp : arraylist)

Can I loop a HashMap by using the similar method?

2

6 Answers

You can iterate over the keys, entries or values.

for (String key : map.keySet()) { String value = map.get(key);
}
for (String value : map.values()) {
}
for (Map.Entry<String,String> entry : map.entrySet()) { String key = entry.getKey(); String value = entry.getValue();
}

This is assuming your map has String keys and String values.

1

You can't directly loop a Map like that in Java.

You can, however, loop the keys:

for (SomeKeyObject key : map.keySet())

The values:

for (SomeValueObject value : map.values())

Or even its entries:

for (Map.Entry<SomeKeyObject, SomeValueObject> entry : map.entrySet())

you can do

for (String key : hashmap.keySet()) { String value = hashmap.get(key);
}

You can do it by using an Iterator .

 HashMap<String, String> yourHashMap = new HashMap<>(); Iterator<Map.Entry<String, String>> it = yourHashMap.entrySet().iterator(); while(it.hasNext()){ it.next(); System.out.println(yourHashMap.get(it)); }

At first sight it might be tempting to use a for-loop instead of an Iterator, but

you will need an Iterator if you want to modify the elements in your HashMap while iterating over them!

When using a for-loop you cannot remove elements from your map while

 it.remove()

would work well in the above example.

public class IterableHashMap<T,U> extends HashMap implements Iterable { @Override public Iterator iterator() { // TODO Auto-generated method stub return this.keySet().iterator(); } } public static void main(String[] args) { testA a=new testA(); IterableHashMap test=a.new IterableHashMap<Object,Object>(); for(Object o:test) { } }

Use this

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

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