CODEWITHSUNDEEP
javaarrays
user1014224
user1014224

Reputation: 13

add elements from one array to "empty array"

I'm new to arrays in java, so my question might seem simple to all of u

I have two arrays:

int[] newarray = new int[] {1,2,3,4}  
int[] result = new int[4]  // array with space for 4 elements
i=0

My question is: How do I add elements from newarray to result? For example, how do i add newarray[i]? There seems to be no add function like in python unless you use ArrayLists. Also is it possible to add elements from an array to an arraylist, or doesn't they work together? Hope to get some clarification :)

Upvotes: 1

Views: 8088

Answers (7)

helpermethod
helpermethod

Reputation: 62155

This should also work:

Arrays.asList(result).addAll(Arrays.asList(newarray));

Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.)

Using static imports:

asList(result).addAll(asList(newarray));

Upvotes: 0

Hot Licks
Hot Licks

Reputation: 47729

Either copy elements one at a time in a loop or use System.arraycopy.

Understand that an array in Java is like an array in C in that it's fixed length (there are other classes like ArrayList for variable-length use). So you don't "add" a new element, you simply assign a value (x[i] = something;) to an existing element (which was initialized to zero when the array was created).

To my knowledge there's no "add all elements of this array" method on ArrayList, so to do that you'd have to loop through the array and add the elements one at a time. There are methods to go the other direction.

Upvotes: 0

Sebastian Paaske Tørholm
Sebastian Paaske Tørholm

Reputation: 50858

To set the ith element in result to the ith element in newarray, do the following:

result[i] = newarray[i];

In addition, you can copy over the entirety of the array using arraycopy:

System.arraycopy(newarray, 0, result, 0, newarray.length);

See also:

Upvotes: 6

Jan Vorcak
Jan Vorcak

Reputation: 19989

System.arraycopy(newarray, 0, result, 0, newarray.length);

or you can do it manually 

for(int i = 0; i < newarray.length; i++) {
    result[i] = newarray[i];
}

to work with Arrays, you can use

Arrays.asList(Object[] a);

Upvotes: 0

shift66
shift66

Reputation: 11958

        int[] newarray = new int[] {1,2,3,4}  
        int[] result = new int[newarray.length];
        for(int i=0;i<newarray.length;i++)
            result[i]=newarray[i];

Upvotes: 1

Kasper Elbo
Kasper Elbo

Reputation: 178

Lets say you want to assign the third value in newarray to the third index in result. That would be like:

result[2] = newarray[2]

Upvotes: 0

Rafael Steil
Rafael Steil

Reputation: 4697

Use System.arrayCopy to copy arrays. Example:

System.arraycopy(newarray, 0, result, 0, newarray.length)

The first argument is the source array, then the source position, then the destination array and destination position, and the length.

Upvotes: 1

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