CODEWITHSUNDEEP
java
Liondancer
Liondancer

Reputation: 16469

copying portion of object array in Java

If I have an object array in Java Car[] a = {0,1,2,3,4,5,6,7}. How would I make a copy of this array from index 2 to 7?

I thought about making a for loop

Car[] b = new Car[a.length - 2];

for (int i = 2; i < a.length; i++) {
  b[i - 2] = a[i];
}

Is there another way by using some of Java's built in Library? If there is, would it be more or less efficient than the for loop I proposed?

Upvotes: 2

Views: 843

Answers (7)

william.eyidi
william.eyidi

Reputation: 2365

CopiesofRange() of the Arrays seems to be a recommended method to perform a copy of a specified range into another array.

Signature

public static <T> T[] copyOfRange(T[] original,
                  int from,
                  int to)

T is generic and can be replaced by any class or primary type of variables.

Upvotes: 1

Elliott Frisch
Elliott Frisch

Reputation: 201439

If I have an object array in Java Car[] a = {0,1,2,3,4,5,6,7}. How would I make a copy of this array from index 2 to 7?

Use one of the Arrays.copyOfRange() methods like Arrays.copyOfRange(T[], int, int),

Car[] b = Arrays.copyOfRange(a, 2, 7);

From the Javadoc,

Copies the specified range of the specified array into a new array.

It is also possible to use System.arraycopy(Object,int,Object,int,int),

Car[] b = new Car[a.length - 2];
System.arraycopy(a, 2, b, 0, b.length);

And its Javadoc,

Copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.

Upvotes: 2

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41200

Arrays#copyOfRange - Copies the specified range of the specified array into a new array.

java.util.Arrays.copyOfRange(copyFrom, startindex, endIndex);

Arrays#copyOfRange method internally use System#arraycopy. Source for reference

AND alternatively you can use System utility it also.

System#arraycopy(Object src, int srcPos, Object dest, int destPos, int length) -

Upvotes: 4

Runcorn
Runcorn

Reputation: 5224

You can use 

Car[] splitArray = Arrays.copyOfRange(a, starting_index, end_index);

Upvotes: 3

morgano
morgano

Reputation: 17422

System arraycopy:

System.arraycopy(a, 2, b, 0, 5);

where b is your destination, starting from index 2, taking 5 (up to position 7)

Upvotes: 4

Octavia Togami
Octavia Togami

Reputation: 4296

You can use the Arrays class:

b = Arrays.copyOfRange(a, 2, 7);

Upvotes: 4

Rod_Algonquin
Rod_Algonquin

Reputation: 26198

You can use the copyOfRange of the Arrays class to copy certain ranges.

sample:

Arrays.copyOfRange(b, 2, 7);

Method implementation

copyOfRange(T[] original,
              int from,
              int to)

Upvotes: 5

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