使用克隆方法而不捕获CloneNotSupportedException

Question

I know that when using the clone method you're supposed to catch the CloneNotSupportedException. However, I recently tried to clone an array of random integers just by invoking .clone( ) on the array, and it worked! No try-catch block was necessary. The code was something like this:

import java.util.Arrays;
import java.util.Random;

public class ClonePractice
{
    public static void main(String[ ] args)
    {
        int[ ] A = new int[100];

        Random random = new Random( );

        for( int i = 0; i < 100; i++ )
            A[i] = 1 + random.nextInt(100); //Get random integer between 1 and 100.

        int[ ] B = A.clone( );

        B[0] = 1000;

        System.out.println( Arrays.toString(A) );

        System.out.println( Arrays.toString(B) );

        // Arrays A and B should have different first values because they are
        // independent objects in memory.

    } // End of main method.

}  // End of ClonePractice class.

This code compiles and runs beautifully! But it does not require catching the CloneNotSupportedException inside a try-catch block. Could someone please explain why this is the exception to the "rule" about catching that exception. Thank you!!!

Answer 1

The javadoc for Object.clone() says:

Note that all arrays are considered to implement the interface Cloneable

Since the compiler knows that arrays are always cloneable, it knows that clone() on an array will not raise CloneNotSupportedException . It doesn't make that assumption for other Cloneable classes, but arrays as usual seem to be dealt with as a special case.

Answer 2

This is by definition. The Java language specification says :

10.7. Array Members
The members of an array type are all of the following:
...
The public method clone, which overrides the method of the same name in class Object and throws no checked exceptions.