How to create a general placeholder function in Java and use the function as a parameter later?

I don't know how to express my question, but it's simple I want to create a generic placeholder function that takes a parameter from an existing function Let me give you an example For simplicity, suppose I want to know how long a function takes to execute in milliseconds

public class Example{
   public static void main(String[] args) {
      int arr[] = {30,8,21,19,50,...,n};
      //needs to accept a function with a parameter as an argument.
      tiMetakenFunc(foo(arr),arr);
      tiMetakenFunc(bar(arr),arr);
   }

   public static void foo(int A[]){
     //do stuff
   }

   public static void bar(int A[]){
     //do stuff
   } 

   public static void tiMetakenFunc(/*what goes here?*/,int A[]){
      long startTime = System.nanoTime();

      //placeholder for foo and bar function here
      placeholder(A);

      long endTime = System.nanoTime();
      long duration = ((endTime - startTime) / 1000000);
      System.out.println("function took: " + duration + "milliseconds");

   }
}

If you need to express my question better, please feel free to edit my question

Solution

Using java 8 Lambdas and functional interfaces, you can accept runnable, which performs some general, unspecified operations

public static void tiMetakenFunc(Runnable func) {
  long startTime = System.nanoTime();

  //placeholder for foo and bar function here
  func.run();

  long endTime = System.nanoTime();
  long duration = ((endTime - startTime) / 1000000);
  System.out.println("function took: " + duration + "milliseconds");
}

Then you call it:

tiMetakenFunc(() -> foo(arr));
tiMetakenFunc(() -> bar(arr));

This is the abbreviation of the former lambda equivalent:

tiMetakenFunc(new Runnable() {
    @Override public void run() {
        foo(arr);
    }
});
tiMetakenFunc(new Runnable() {
    @Override public void run() {
        bar(arr);
    }
});

I deleted the int [] a parameter because it is not necessarily needed here As you can see, arr can be embedded in runnable If you want to keep it as a parameter, you can switch from runnable to consumer < int [] >

public static void tiMetakenFunc(Consumer<int[]> func,int[] A) {
  long startTime = System.nanoTime();

  //placeholder for foo and bar function here
  func.accept(A);

  long endTime = System.nanoTime();
  long duration = ((endTime - startTime) / 1000000);
  System.out.println("function took: " + duration + "milliseconds");
}

tiMetakenFunc(arr -> foo(arr),A);
tiMetakenFunc(arr -> bar(arr),A);

Or, using method references with::, you can write:

tiMetakenFunc(Example::foo,A);
tiMetakenFunc(Example::bar,A);

Both are equivalent to this pre lambda Code:

tiMetakenFunc(new Consumer<int[]>() {
    @Override public void accept(int[] arr) {
        foo(arr);
    }
});
tiMetakenFunc(new Consumer<int[]>() {
    @Override public void accept(int[] arr) {
        bar(arr);
    }
});