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How to update a value, given a key in a hashmap?
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Problem
Suppose we have a
How do I update (increment) the integer-value of the string-key for each existence of the string I find?
One could remove and reenter the pair, but overhead would be a concern.
Another way would be to just put the new pair and the old one would be replaced.
In the latter case, what happens if there is a hashcode collision with a new key I am trying to insert? The correct behavior for a hashtable would be to assign a different place for it, or make a list out of it in the current bucket.
HashMap in Java.How do I update (increment) the integer-value of the string-key for each existence of the string I find?
One could remove and reenter the pair, but overhead would be a concern.
Another way would be to just put the new pair and the old one would be replaced.
In the latter case, what happens if there is a hashcode collision with a new key I am trying to insert? The correct behavior for a hashtable would be to assign a different place for it, or make a list out of it in the current bucket.
Solution
map.put(key, map.get(key) + 1);should be fine. It will update the value for the existing mapping. Note that this uses auto-boxing. With the help of
map.get(key) we get the value of corresponding key, then you can update with your requirement. Here I am updating to increment value by 1.Code Snippets
map.put(key, map.get(key) + 1);Context
Stack Overflow Q#4157972, score: 1235
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