49592

Insert array into another array

Question:

Writing method to insert a[] into numbers[] at a position stored in variable "location".

public boolean insertArray(int location, double a[]) { if (length != MAX_CAPACITY) { numbers[location] = a[]; length++; return true; } return false; }

Is it possible to pass through an array?

Answer1:

You can use <a href="https://docs.oracle.com/javase/7/docs/api/java/lang/System.html#arraycopy(java.lang.Object,%20int,%20java.lang.Object,%20int,%20int)" rel="nofollow">System.arraycopy</a> :

public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length) <hr />

Here is a simple example you can follow to solve your problem :

double a[] = {1, 2, 3, 4, 5}; double b[] = {6, 7, 8}; int local = 5; double result[] = new double[a.length + b.length]; System.arraycopy(a, 0, result, 0, a.length); System.arraycopy(b, 0, result, local, b.length); System.out.println(Arrays.toString(result));

<strong>Output</strong>

[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0]

Answer2:

<strong>Yes, you can.</strong>

But the Array has to be a Two dimensions Array! Example:

public static double[][] numbers = new double[MAX_CAPACITY][]; public boolean insertArray(int location, double[] a) { if (length != MAX_CAPACITY) { numbers[location] = a; length++; return true; } return false; }

Answer3:

You can utilise Arrays too.

int[] numbers = ... int[] a = ... int n = numbers.length; numbers = Arrays.copyOf(numbers, numbers.length + a.length); System.arraycopy(a, 0, numbers, n, a.length);

In general List and ArrayList are better abstractions with almost the same efficiency.

Answer4:

<blockquote>

Is there a specific reason you're using arrays instead of a List, such as an ArrayList?

</blockquote>

If you're using a java.util.List, then use <a href="https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html#addAll%28int,%20java.util.Collection%29" rel="nofollow">List.addAll(int location, Collection a)</a>.

If you're using arrays, then you'll need to perform the array allocation and copying yourself. Here's an <a href="http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/ArrayList.java#ArrayList.addAll%28int%2Cjava.util.Collection%29" rel="nofollow">example implementation</a> of ArrayList.addAll(int, Collection) from OpenJDK:

// Copyright 1997-2007 Sun Microsystems, Inc. public boolean addAll(int index, Collection<? extends E> c) { rangeCheckForAdd(index); Object[] a = c.toArray(); int numNew = a.length; ensureCapacity(size + numNew); // Increments modCount int numMoved = size - index; if (numMoved > 0) System.arraycopy(elementData, index, elementData, index + numNew, numMoved); System.arraycopy(a, 0, elementData, index, numNew); size += numNew; return numNew != 0; }

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