For example, I can loop an ArrayList like this
for (String temp : arraylist)
Can I loop a HashMap by using the similar method?
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.
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));
