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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6. import java.util.function.Function;
  7.  
  8. /* Name of the class has to be "Main" only if the class is public. */
  9. class Ideone
  10. {
  11.     public static void main(String[] args) {
  12.  
  13.         HashMap<SomeClass, Integer> myMap = new HashMap<SomeClass, Integer>() {{
  14.             put(new SomeClass(2, 26), 10);
  15.             put(new SomeClass(8, 25), 5);
  16.             put(new SomeClass(5, 24), 5);
  17.         }};
  18.  
  19.         float resultOne = average(myMap, SomeClass::getMyInt);
  20.         float resultTwo = average(myMap, SomeClass::getAge);
  21.         System.out.println(resultOne);
  22.         System.out.println(resultTwo);
  23.     }
  24.  
  25.     public static float average(HashMap<SomeClass, Integer> myMap, Function<SomeClass, Integer> getterFunc) {
  26.  
  27.         float totalAmount = 0;
  28.         float buffer = 0;
  29.         for (SomeClass aClass : myMap.keySet()) {
  30.             totalAmount += myMap.get(aClass);
  31.             buffer += getterFunc.apply(aClass) * myMap.get(aClass);
  32.         }
  33.         return buffer / (totalAmount * myMap.size());
  34.     }
  35.  
  36.     public static class SomeClass {
  37.  
  38.         private final int myInt;
  39.  
  40.         private final int age;
  41.  
  42.         public SomeClass(int myInt, int age) {
  43.  
  44.             this.myInt = myInt;
  45.             this.age = age;
  46.         }
  47.  
  48.         public int getAge() {
  49.  
  50.             return age;
  51.         }
  52.  
  53.         public int getMyInt() {
  54.  
  55.             return myInt;
  56.         }
  57.     }
  58. }
Success #stdin #stdout 0.08s 33792KB
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1.4166666
8.416667
https://ideone.com/SsgLOE
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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