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Simplifying Nested Loops With Java 8 Lambdas

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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 ·
Free Resource

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.

Topics:
java 8 ,lambdas ,nested loops

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