Solution with Java streams and Functional Interface

src/com/demo/exercises/MaxPrimeNumDifferenceV8.java

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+package com.demo.exercises;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+import java.util.function.BiFunction;
+import java.util.function.IntPredicate;
+import java.util.function.IntUnaryOperator;
+import java.util.stream.IntStream;
+
+public class MaxPrimeNumDifferenceV8 {
+
+    public static void main(String[] args) {
+        MaxPrimeNumDifferenceV8 code = new MaxPrimeNumDifferenceV8();
+        code.readInputsAndProcess();
+    }
+
+    private void readInputsAndProcess(){
+        try {
+            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+			StringTokenizer tokenizer = new StringTokenizer(br.readLine());
+            int _testCases = Integer.parseInt(tokenizer.nextToken());           
+			int cnt = 0;
+            while(cnt< _testCases){
+                final long startTime = System.nanoTime()/1000000;
+                String[] numRange = br.readLine().split(" ");
+                final int[] primes = new int[2];
+
+                primes[0] = findMinPrimeNumberInRange.apply(Integer.parseInt(numRange[0]), Integer.parseInt(numRange[1]));
+                primes[1] = findMaxPrimeNumberInRange.apply(Integer.parseInt(numRange[0]), Integer.parseInt(numRange[1]));
+
+                if(primes[0] == 0 && primes[1]==0){
+                    System.out.println(-1);
+                } else if(primes[1] == 0){
+                    System.out.println(0);
+                } else{
+                    System.out.println(primes[1]-primes[0]);
+                }
+                final long endTime = System.nanoTime()/1000000;
+                System.out.println("Time Taken for input(ms)"+(cnt+1)+"==>"+(endTime-startTime));
+                cnt++;               
+            }
+
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    final IntPredicate isPrime = (num) -> {
+        int count = 0;
+        int i=1;
+        while(i<=num){
+            if(num%i == 0){
+                count++;
+            }
+            i++;
+        }
+
+        if(count == 2){
+            return true;
+        }
+        return false;
+     };
+
+    final BiFunction<Integer, Integer, Integer> findMinPrimeNumberInRange = (start, end) -> {
+        return IntStream.rangeClosed(start, end)
+        .filter(isPrime)
+        .findFirst()
+        .orElse(0);        
+    };
+
+    final IntUnaryOperator postiveValue = (num) -> -1 * num;
+
+    final BiFunction<Integer, Integer, Integer> findMaxPrimeNumberInRange = (start, end) -> {
+        return IntStream.rangeClosed(-end, -start)
+        .map(postiveValue)
+        .filter(isPrime)
+        .findFirst()
+        .orElse(0);
+    };
+}