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Use Intellij to visualize debugging Stream operation

Last time I talked about the stream API feature in Java 8. It is a very good new feature, but unlike previously looping code, single-step debugging does not work for stream API. Luckily, IntelliJ IDEA provides a tool for us to visualize the stream code.

Example code:

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List<Integer> numbers2 = Arrays.asList(1, 2, 3, 4, 5, 6, 7);

numbers2.stream()
    .map(x -> x * x)
    .filter(x -> x % 3 == 0)
    .forEach(System.out::println);

Add a break point at the last line of stream

Start debug, and find the button in debug interface

Wait for a few seconds, you can see the results of each step of the stream operation