10.7

Array Members

ARRAYS

class A implements Cloneable {

public final int length =

X

;

public Object clone() {

try {

return super.clone();

} catch (CloneNotSupportedException e) {

throw new InternalError(e.getMessage());

}

}

}

Every array implements interface

Cloneable

. That arrays are cloneable is shown

by the test program:

class Test {

public static void main(String[] args) {

int ia1[] = { 1, 2 };

int ia2[] = (int[])ia1.clone();

System.out.print((ia1 == ia2) + " ");

ia1[1]++;

System.out.println(ia2[1]);

}

}

which prints:

false 2

showing that the components of the arrays referenced by

ia1

 and

ia2

 are different

variables. (In some early implementations of Java this example failed to compile

because the compiler incorrectly believed that the clone method for an array could

throw a

CloneNotSupportedException

.)

A

clone

 of a multidimensional array is shallow, which is to say that it creates

only a single new array. Subarrays are shared, as shown by the example program:

class Test {

public static void main(String[] args) throws Throwable {

int ia[][] = { { 1 , 2}, null };

int ja[][] = (int[][])ia.clone();

System.out.print((ia == ja) + " ");

System.out.println(ia[0] == ja[0] && ia[1] == ja[1]);

}

}

which prints:

false true

showing that the

int[]

 array that is

ia[0]

 and the

int[]

 array that is

ja[0]

 are

the same array.

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