Get predecessor key from map using java

I have a map in this

 TreeMap<Integer, Float> matrixMap = new TreeMap<Integer, Float>(); 

Results in

{12=0.4, 24=0.63, 36=0.86, 48=1.12, 60=1.39, 72=1.67, 84=1.98, 96=2.31, 108=3.3, 120=3.84, 132=4.4, 144=5.0, 156=5.62, 168=6.28, 180=6.97, 192=7.34, 204=7.74, 216=8.15, 228=8.07, 240=8.33} 

Now, I want fetch a value of a key 25. Ideally 25 is not available in the result. So, I want to get values of 24 & 36.

duration = 25 

I'm able to get the value of 36, but how can I get the predecessor of 36.

for(Map.Entry<Integer, Float> entry : matrixMap.entrySet()) { if(duration < entry.getKey()) { max = entry.getValue(); break; } } 

How to get immediate predecessor value too(24 key in this case)?

Any ideas

2 Answers

To get the value of the first key >= 25:

matrixMap.tailMap(25).values().next() 

or:

matrixMap.get(matrixMap.tailMap(25).firstKey()) 

To get the value of the first key <= 25:

matrixMap.get(matrixMap.headMap(25).lastKey()) 

I've solved using the following way.

int above = matrixMap.ceilingKey(duration); int below = matrixMap.floorKey(duration); logger.info("above="+above+", below="+below); min = insuranceMatrixMap.get(below); max = insuranceMatrixMap.get(above);