Java8Sample3.java

interface ConditionCheck<T> {
	public boolean check(T i);
}

class MathUtility<T extends Number> {
	public static <T extends Number> Number sum(List<T> list, ConditionCheck<T> condition){
		//ability to add is only here
		
		Number sum = 0;
		for(T i: list){
			if(condition.check(i)){
				if (i instanceof Integer) {
					sum=sum.intValue()+i.intValue();
				}
				if(i instanceof Double) {
					sum=sum.doubleValue()+i.doubleValue();
				}
				//so on
			}
		}
		return sum;
	}
}

//In client

ConditionCheck isEven = new ConditionCheck<Integer>(){
	@Override
	public boolean check(Integer i) {
		return i%2==0;
	}	
};

int result = MathUtility.sum(listOfInts, isBig))