Updating a java map entry

JavaMapIn Place

Java Problem Overview


I'm facing a problem that seems to have no straighforward solution.

I'm using java.util.Map, and I want to update the value in a Key-Value pair.

Right now, I'm doing it lik this:

private Map<String,int> table = new HashMap<String,int>();
public void update(String key, int val) {
    if( !table.containsKey(key) ) return;
    Entry<String,int> entry;
    for( entry : table.entrySet() ) {
        if( entry.getKey().equals(key) ) {
            entry.setValue(val);
            break;
        }
    }
}

So is there any method so that I can get the required Entry object without having to iterate through the entire Map? Or is there some way to update the entry's value in place? Some method in Map like setValue(String key, int val)?

jrh

Java Solutions


Solution 1 - Java

Use

table.put(key, val);

to add a new key/value pair or overwrite an existing key's value.

From the Javadocs:

> V put(K key, V value): Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

Solution 2 - Java

If key is present table.put(key, val) will just overwrite the value else it'll create a new entry. Poof! and you are done. :)

you can get the value from a map by using key is table.get(key); That's about it

Solution 3 - Java

You just use the method

public Object put(Object key, Object value)

if the key was already present in the Map then the previous value is returned.

Attributions

All content for this solution is sourced from the original question on Stackoverflow.

The content on this page is licensed under the Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.

Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionjrharshathView Question on Stackoverflow
Solution 1 - JavaskaffmanView Answer on Stackoverflow
Solution 2 - JavaPriyankView Answer on Stackoverflow
Solution 3 - JavamkoellerView Answer on Stackoverflow