Get index or key given the value in java Map

 

Given the value, I need to get the index or key which this value belongs in a Map without the need to iterate it. I'm using java.

Thanks

Guava has a BiMap, which is a bidirectional map (each key and each value are unique).

If you don't waht to use an external library, you only have 2 options:

  • use a plain HashMap and you will need to iterate over the keys
  • use 2 hashmaps, one relating keys to values, and one relating values to keys (which in essence is what a bidirectional map does).

    • You could always use a BidiMap from commons-collections:

    http://commons.apache.org/collections/apidocs/org/apache/commons/collections/BidiMap.html

    You have to use some kind of BidirectionalMap . For example this one: http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/BiMap.html

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