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If you are writing a development tool such as an application builder, you may want to allow the end user to create arrays at runtime. Your program can provide this capability by invoking theArray.newInstance
method.The following sample program uses the
newInstance
method to create a copy of an array that is twice the size of the original array. ThenewInstance
method accepts as arguments the length and component type of the new array. The source code follows:The output of the preceding program is:import java.lang.reflect.*; class SampleCreateArray { public static void main(String[] args) { int[] originalArray = {55, 66}; int[] biggerArray = (int[]) doubleArray(originalArray); System.out.println("originalArray:"); for (int k = 0; k < Array.getLength(originalArray); k++) System.out.println(originalArray[k]); System.out.println("biggerArray:"); for (int k = 0; k < Array.getLength(biggerArray); k++) System.out.println(biggerArray[k]); } static Object doubleArray(Object source) { int sourceLength = Array.getLength(source); Class arrayClass = source.getClass(); Class componentClass = arrayClass.getComponentType(); Object result = Array.newInstance(componentClass, sourceLength * 2); System.arraycopy(source, 0, result, 0, sourceLength); return result; } }You can also use theoriginalArray: 55 66 biggerArray: 55 66 0 0newInstance
method to create multidimensional arrays. In this case, the parameters of the method are the component type and an array ofint
types representing the dimensions of the new array.The next sample program shows how to use
newInstance
to create multidimensional arrays:import java.lang.reflect.*; class SampleMultiArray { public static void main(String[] args) { // The oneDimA and oneDimB objects are one // dimensional int arrays with 5 elements. int[] dim1 = {5}; int[] oneDimA = (int[]) Array.newInstance(int.class, dim1); int[] oneDimB = (int[]) Array.newInstance(int.class, 5); // The twoDimStr object is a 5 X 10 array of String objects. int[] dimStr = {5, 10}; String[][] twoDimStr = (String[][]) Array.newInstance(String.class,dimStr); // The twoDimA object is an array of 12 int arrays. The tail // dimension is not defined. It is equivalent to the array // created as follows: // int[][] ints = new int[12][]; int[] dimA = {12}; int[][] twoDimA = (int[][]) Array.newInstance(int[].class, dimA); } }
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