Core Java

Simplifying nested loops with Java 8 Lambdas

This is just a quick tip for everyone who often 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.

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Michael Scharhag

Michael Scharhag is a Java Developer, Blogger and technology enthusiast. Particularly interested in Java related technologies including Java EE, Spring, Groovy and Grails.
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6 years ago

Hi Michael,

Thank you for this article. Is it possible to ask you an advice regarding nested for loop with java 8. Thank you very much. Jade

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