Logical indexing in JAVA

debugcn 投稿 Dev

Likeunknown

How to do access array elements using logical indexing in Java?

Matlab/Octave equivalent of what I want to do:

A = [1 2 3 4 5 6]
logicalarray=[0 1 0 0 0 1];
result= A(logical)

which gives result =[2 6]

If I have the same A and logicalarray in Java. How would I get that result without using loops?

SubOptimal

As said by @Oleg you have a complete different syntax in Java and as @luk2302 mention you might use Streams

Following snippet

int[] a = {1, 2, 3, 4, 5, 6};

// logicalarray=[0 1 0 0 0 1];
// index is zero-based in Java
int[] result = IntStream.of(1, 5)
        .map(i -> a[i])
        .toArray();

System.out.println("result = " + Arrays.toString(result));

would print

result = [2, 6]

edit If you need to keep the logicalarray a possible solution could be

int[] a = {1, 2, 3, 4, 5, 6};
int[] logicalarray = {0, 1, 0, 0, 0, 1};
int[] result = IntStream.range(0, logicalarray.length) // create a stream of array indexes
        .filter(i -> logicalarray[i] == 1) // filter the indexes which are 1 in logicalarray
        .map(i -> a[i]) // map the related value from array a
        .toArray(); // create an array of the values
System.out.println("result = " + Arrays.toString(result));

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