Reuse code for looping through multidimensional-array

Question

Let's say I have a multi-dimensional array as a member of a class and a lot of methods, that loop through every element of the array and then operate on it. The code might look like this:

public class Baz {

    private Foo[][] fooArray = new Foo[100][100];

    public Baz() {
        for (int i = 0; i < fooArray.length; i++) {
            for (int j = 0; j < fooArray[i].length; j++) {
                // Initialize fooArray
            }
        }
    }

    public void method1() {
        for (int i = 0; i < fooArray.length; i++) {
            for (int j = 0; j < fooArray[i].length; j++) {
                // Do something with fooArray[i][j] 
            }
        }
    }

    public void method2() {
        for (int i = 0; i < fooArray.length; i++) {
            for (int j = 0; j < fooArray[i].length; j++) {
                // Do something else with fooArray[i][j] 
            }
        }
    }

    // and so on
}

Now, since the code for the loop is always the same, only the operation within the loop changes, is there any way the code for looping could be somehow refactored into a seperate method? It would be so nice to be able to do

doInLoop(functionToExecute());

What would be the nearest substitute for doing something like this, if it is even possible?

Answer 1

What you are looking for is the Command pattern: define a single-method interface and implement it for each use case as an anonymous class. You'll pass an instance of this interface to a method which does all the boilerplate and calls your method just for the interesting part:

public void forAllMembers(Foo[][] fooArray, Command c) {
    for (int i = 0; i < fooArray.length; i++) {
        for (int j = 0; j < fooArray[i].length; j++) {
            c.execute(fooArray[i][j]);
        }
    }
}

Or, wait for Java 8, which will introduce Lambdas and will give your problem a first-class solution!