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// ArrayTest: How well do you understand arrays?
// Written 2003 by Wayne Pollock, Tampa Florida USA

class ArrayTest
   public static void main ( String [] args )
      int [] array = { 'H', 'e', 'l', 'l', 'o' };
      byte [] barray = { 'H', 'e', 'l', 'l', 'o' };
      char [] carray = { 'H', 'e', 'l', 'l', 'o' };

      // Will this work, fail to compile, or throw an Exception?
      int [] copy = (int[]) array.clone();

      // What is the output?

      System.out.println( array );
      System.out.println( barray );
      System.out.println( carray );

See the Answer


Although java.lang.System.arraycopy can be used to flexibly copy arrays, all arrays support the Clonable interface.  So array.clone() works just fine to copy a whole array.

As for the output statements, when any object is printed Java auto-magically invokes that object's toString method.  Most objects use the inherited Object.toString() method, which prints out a unique string for each object.  This string contains the class name (which for arrays of primitive types can look quite strange), an '@' (at-sign), and a hexidecimal number (the hashcode of the object).

For array and barray, it is this Object.toString() method that gets used.  However char arrays use a custom toString method that displays the sequence of characters in the array as a String.  So the output of this program is something like this (actual hex numbers may vary from what you see if you run this program):


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