如何在java中将我的HashMap Key从float转换为Integer？

Question

import java.util.Map;
import java.util.HashMap;

public class q9 {
public static void main(String[] args) {
    Map<Float, String> map1 = new HashMap<>();
    Map<Integer, String>map2= new HashMap<>();

I want to convert my all map1 keys from float to Integer.

    map1.put(11.1f, "black");
    map1.put(12.1f, "brown");
    map1.put(13.1f, "Grey");
    map1.put(14.1f, "blue");

In this, I want to store map1 HashMap to map2 HashMap but map2 has an Integer type key and map1 has a float type key and hence I want to convert my map1 keys to Integer. So I can easily store those keys into map2

map2.putAll(map1);



  }

}

Answer 1

You can iterate over map1 and insert each entry to map2 after changing the key to an Integer :

for(Map.Entry<Float, String> entry : map1.entrySet()) 
  map2.put(entry.getKey().intValue(), entry.getValue()); 

Answer 2

Iterate the entries and cast the key value.

for (Map.Entry<Float, String> entry : map1.entrySet()) {
    map2.put((int)(float)entry.getKey(), entry.getValue());
}

We need to double-cast to trigger float auto-unboxing and int auto-boxing.

Alternative is it unbox directly to int manually, and let the compiler auto-box that.

for (Map.Entry<Float, String> entry : map1.entrySet()) {
    map2.put(entry.getKey().intValue(), entry.getValue());
}

Warning: If two or more float values converts to the same int value, it is arbitrary which entry wins. That is the nature of HashMap ordering.