Using the keySet() method in HashMap

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I have a method that goes through the possible states in a board and stores them in a HashMap

void up(String str){
  int a = str.indexOf("0");
  if(a>2){
   String s = str.substring(0,a-3)+"0"+str.substring(a-2,a)+str.charAt(a-3)+str.substring(a+1);
   add(s,map.get(str)+1);
   if(s.equals("123456780")) {
    System.out.println("The solution is on the level  "+map.get(s)+" of the tree");

        //If I get here, I need to know the keys on the map
       // How can I store them and Iterate through them using 
      // map.keySet()?

   }
  }

}

I'm interested in the group of keys. What should I do to print them all?

HashSet t = map.keySet() is being rejected by the compiler as well as

LinkedHashSet t = map.keySet()

Use:

Set<MyGenericType> keySet = map.keySet();

Always try to specify the Interface type for collections returned by these methods. This way regardless of the actual implementation class of the Set returned by these methods (in your case map.keySet()) you would be ok. This way if the next release the jdk guys use a different implementation for the returned Set your code will still work.

map.keySet() returns a View on the Keys of the map. Making changes to this view results in changing the underlying map though those changes are limited. See the javadoc for Map:

http://java.sun.com/j2se/1.5.0/docs/api/java/util/Map.html#keySet%28%29

Hashmap methods in Java with Examples, Description. The keySet() method is used to get a Set view of the keys contained in this map. Declaration. Following is the declaration for java.util.HashMap. The keySet() method is used to get a Set view of the keys contained in this map. Declaration Following is the declaration for java.util.HashMap.keySet() method.

Map<String, String> someStrings = new HashMap<String, String>();
for(Map.Entry<String, String> entry : someStrings.entrySet()) {
    String key = entry.getKey();
    String value = entry.getValue();
}

This is how I like to iterate through Maps. If you specifically want just the keySet(), that answer is elsewhere on this page.

java.util.HashMap.keySet() Method, This way if the next release the jdk guys use a different implementation for the returned Set your code will still work. map.keySet() returns a  From Javadocs HashMap has several methods that can be used to manipulate and extract data from a hasmap. public Set<K> keySet() Returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

for ( String key : map.keySet() ) { 
 System.out.println( key );
}

Using the keySet() method in HashMap, On this document we will be showing a java example on how to use the keySet() method of HashMap Class. Basically this method is to get all  This is the inherent behavior of keySet() method when you modify the HashMap object the set would also be modified. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations.

Set t = map.ketSet()

The API does not specify what type of Set is returned.

You should try to declare variables as the interface rather than a particular implementation.

Java HashMap keySet() method example, If many mappings are to be stored in a HashMap instance, creating it with a sufficiently large capacity will allow the mappings to be Removes the mapping for the specified key from this map if present. int, size() public Set<K> keySet(). The keySet method of the HashMap class returns a Set view of all the keys contained in the map object. The keySet method returns a Set view of all the keys. This view is backed by the original HashMap object.

Just

Set t = map.keySet();

HashMap (Java Platform SE 7 ), Note that using many keys with the same hashCode() is a sure way to slow down performance of any hash table. To ameliorate Constructs a new HashMap with the same mappings as the specified Map. keySet. public Set<K> keySet(). I have used the keySet() method to print out the number of keys within my HashMap, but what I have not done yet is find the length for each word within the HashMap and then print out the number of characters within each word. I am currently unsure as to how I should do this.

HashMap (Java Platform SE 8 ), Best Java code snippets using java.util.HashMap.keySet (Showing top 20 results out public Iterator<String> keyIterator() { if ( values == null ) { return emptyIter; }​  The java.util.HashMap.entrySet() method in Java is used to create a set out of the same elements contained in the hash map. It basically returns a set view of the hash map or we can create a new set and store the map elements into them. Syntax: hash_map.entrySet() Parameters: The method does not take any parameter.

java.util.HashMap.keySet java code examples, in Java. keySet() method returns a view of the keys contained in the map. In this post, we will discuss various methods to iterate Map using keySet() in Java. 43. import java.util.HashMap;. import java.util.Iterator;. import java.util.Map;. One object is used as a key (index) to another object (value). It can store different types: String keys and Integer values, or the same type, like: String keys and String values: Example. Create a HashMap object called capitalCities that will store String keys and String values:

5 ways to Iterate Map using keySet() in Java, You can also use the keySet() method to iterate over a Java HashMap as shown in the following example: // Iterating using keySet() method of HashMap  HashMap Class Methods. Here is the list of methods available in HashMap class. I have also covered examples using these methods at the end of this post. void clear(): It removes all the key and value pairs from the specified Map. Object clone(): It returns a copy of all the mappings of a map and used for cloning them into another map.

Comments
  • To reiterate what he said, if you now do keySet.remove(item), then 'item' will also disappear from 'map'.