Reflection for manipulating arrays in java| java sample codes

Reflection for Manipulating Arrays

import java.lang.reflect.*;

/**

* This program demonstrates the use of reflection for manipulating arrays.

*/

public class ArrayGrowTest

{

public static void main(String[] args)

{

int[] a = { 1, 2, 3 };

a = (int[]) goodArrayGrow(a);

arrayPrint(a);

String[] b = { "Tom", "Dick", "Harry" };

b = (String[]) goodArrayGrow(b);

arrayPrint(b);

System.out.println("The following call will generate an exception.");

b = (String[]) badArrayGrow(b);

}

/**

* This method attempts to grow an array by allocating a new array and copying all elements.

* @param a the array to grow

* @return a larger array that contains all elements of a. However, the returned array has

* type Object[], not the same type as a

*/

static Object[] badArrayGrow(Object[] a)

{

int newLength = a.length * 11 / 10 + 10;

Object[] newArray = new Object[newLength];

System.arraycopy(a, 0, newArray, 0, a.length);

return newArray;

}

/**

* This method grows an array by allocating a new array of the same type and

* copying all elements.

* @param a the array to grow. This can be an object array or a primitive

* type array

* @return a larger array that contains all elements of a.

*/

static Object goodArrayGrow(Object a)

{

Class cl = a.getClass();

if (!cl.isArray()) return null;

Class componentType = cl.getComponentType();

int length = Array.getLength(a);

int newLength = length * 11 / 10 + 10;

Object newArray = Array.newInstance(componentType, newLength);

System.arraycopy(a, 0, newArray, 0, length);

return newArray;

}

/**

* A convenience method to print all elements in an array

* @param a the array to print. It can be an object array or a primitive type array

*/

static void arrayPrint(Object a)

{

Class cl = a.getClass();

if (!cl.isArray()) return;

Class componentType = cl.getComponentType();

int length = Array.getLength(a);

System.out.print(componentType.getName() + "[" + length + "] = { ");

for (int i = 0; i <>

System.out.print(Array.get(a, i) + " ");

System.out.println("}");

}

}

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