Lambda Expression that takes one value and return other

Define functional interface that takes one value and return other.

ProcessorFunction.java

package com.sample.functional.interfaces;

/**
 * Functional interface that takes one value and return other value.
 * 
 * @author krishna
 *
 * @param <T>
 *            Input value type
 * @param <U>
 *            Output value type
 */
public interface ProcessorFunction<T, U> {

 public U process(T obj);
}

Application.java

package com.sample.app;

import java.util.ArrayList;
import java.util.List;

import com.sample.functional.interfaces.ProcessorFunction;

public class Application {

 public static int getNoOfMatchedEle(ProcessorFunction<List<Integer>, Integer> processorFun, List<Integer> list) {
  return processorFun.process(list);
 }

 public static void main(String[] args) {
  List<Integer> input = new ArrayList<>();
  input.add(1);
  input.add(10);
  input.add(21);
  input.add(11);
  input.add(31);

  /* Get total elements */
  int totalEle = getNoOfMatchedEle((list) -> {
   return list.size();
  }, input);

  int eleGreater20 = getNoOfMatchedEle((list) -> {
   int count = 0;
   for (int i : list) {
    if (i > 20)
     count++;
   }
   return count;
  }, input);

  String result1 = String.format("Total elements in the list are %d", totalEle);
  String result2 = String.format("Elements > 20 are %d", eleGreater20);
  
  System.out.println(result1);
  System.out.println(result2);
 }
}

Output

Total elements in the list are 5
Elements > 20 are 2
 

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