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Simplifying Nested Loops With Java 8 Lambdas

A great way to keep looping code out of your main logic in Java 8 apps.

· Java Zone

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This is just a quick tip for everyone who has to work with multi-dimensional arrays in Java 8 (or newer).

In this case, you might often end with code similar to this:

float[][] values = ...
for (int i = 0; i < values.length; i++) {
  for (int k = 0; k < values[i].length; k++) {
    float value = values[i][k];
    // do something with i, k and value
  }
}

If you are lucky, you can replace the loops with for-each loops. However, often the indices are required for computations inside the loop.

In such a case you can come up with a simple utility method that looks like this:

private void loop(float[][] values, BiConsumer<Integer, Integer> consumer) {
  for (int i = 0; i < values.length; i++) {
    for (int k = 0; k < values[i].length; k++) {
      consumer.accept(i, k);
    }
  }
}

We can now loop over array indices like this:

float[][] values = ...
loop(values, (i, k) -> {
  float value = values[i][k];
  // do something with i, k and value
});

This way you can keep the looping code out of your main logic.

Of course, you should change the shown loop() method so it fits your personal needs.

The Java Zone is brought to you in partnership with ZeroTurnaround. Check out this 8-step guide to see how you can increase your productivity by skipping slow application redeploys and by implementing application profiling, as you code!

Topics:
java 8 ,lambdas ,nested loops

Published at DZone with permission of Michael Scharhag, DZone MVB. See the original article here.

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