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How to create a sub array from another array in Java?


Question

How to create a sub-array from another array? Is there a method that takes the indexes from the first array such as:

methodName(object array, int start, int end)

I don't want to go over making loops and making my program suffer.

I keep getting error:

cannot find symbol method copyOfRange(int[],int,int)

This is my code:

import java.util.*;

public class testing 
{
    public static void main(String [] arg) 
    {   
        int[] src = new int[] {1, 2, 3, 4, 5}; 
        int b1[] = Arrays.copyOfRange(src, 0, 2);
    }
}
2015/12/10
1
288
12/10/2015 12:44:11 PM


Arrays.copyOfRange(..) was added in Java 1.6. So perhaps you don't have the latest version. If it's not possible to upgrade, look at System.arraycopy(..)

2010/12/14

Use copyOfRange method from java.util.Arrays class:

int[] newArray = Arrays.copyOfRange(oldArray, startIndex, endIndex);

For more details:

Link to similar question

2017/06/08

Yes, it's called System.arraycopy(Object, int, Object, int, int) .

It's still going to perform a loop somewhere though, unless this can get optimized into something like REP STOSW by the JIT (in which case the loop is inside the CPU).

int[] src = new int[] {1, 2, 3, 4, 5};
int[] dst = new int[3];

System.arraycopy(src, 1, dst, 0, 3); // Copies 2, 3, 4 into dst
2014/09/20

Using Apache ArrayUtils downloadable at this link you can easy use the method

subarray(boolean[] array, int startIndexInclusive, int endIndexExclusive) 

"boolean" is only an example, there are methods for all primitives java types

2015/06/01

JDK >= 1.8

I agree with all the answers above. There is also a nice way with Java 8 Streams:

int[] subArr = IntStream.range(startInclusive, endExclusive)
                        .map(i -> src[i])
                        .toArray();

The benefit about this is, it can be useful for many different types of "src" array and helps to improve writing pipeline operations on the stream.

Not particular about this question, but for example, if the source array was double[] and we wanted to take average() of the sub-array:

double avg = IntStream.range(startInclusive, endExclusive)
                    .mapToDouble(index -> src[index])
                    .average()
                    .getAsDouble();
2020/02/09

Source: https://stackoverflow.com/questions/4439595
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