Contents

Queues and Stacks

Algorithms

Array Adapters

Using a Native Array as a Container

Using a JDK Vector as a Container

One of the primary strengths of JGL is the ability to apply its generic algorithms to JGL containers, native Java arrays, and JDK data structures. The way that it does this is to define the algorithms to accept data structures that implement the Container interface and then to supply special adapter classes that allow native Java arrays and JDK data structures to act as if they were a JGL Container. Here is a diagram that shows all of the JGL array adapters:

This chapter describes the adapter classes for native Java arrays and JDK containers.

Using a Native Java Array as a Container

There is a separate adapter class for each kind of native Java array. When you enumerate a native Java array of primitives using the adapter class, each primitive is automatically retrieved as its closest object equivalent as defined in java.lang. Here is a table that shows this information for each type:

Native Array Type	Adapter Class	Retrieved As
boolean[]	BooleanArray	Boolean
byte[]	ByteArray	Integer
char[]	CharArray	Character
short[]	ShortArray	Integer
int[]	IntArray	Integer
long[]	LongArray	Long
float[]	FloatArray	Float
double[]	DoubleArray	Double
Object[]	ObjectArray	N/A

The adapter classes implement all of the methods defined by the Sequence interface. Because the size of a native Java array is fixed, the add(), clear(), pushBack(), popBack(), pushFront(), popFront(), and remove() methods will always throw an InvalidOperationException. The following example uses an IntArray adapter class to conveniently print, sort, and shuffle a native Java array of ints.

// Copyright(c) 1996,1997 ObjectSpace, Inc.
import COM.objectspace.jgl.*;

public class Adapters1
  {
  public static void main( String[] args )
    {
    int ints[] = { 3, -1, 2, -3, 4 };
    IntArray intArray = new IntArray( ints );
    System.out.println( "Unsorted native int array = " + intArray );

    Sorting.sort( intArray );
    System.out.println( "Sorted = " + intArray );

    Shuffling.randomShuffle( intArray );
    System.out.println( "Randomized = " + intArray );

    for ( int i = 0; i < ints.length; i++ )
      System.out.print( ints[ i ] + " " );
    System.out.println();
    }
  }

Output

Unsorted native int array = int[]( 3, -1, 2, -3, 4 )
Sorted = int[]( -3, -1, 2, 3, 4 )
Randomized = int[]( -1, -3, 4, 2, 3 )
-1 -3 4 2 3 

Using a JDK Vector as a Container

The VectorArray adapter class allows a JDK Vector to act as if it were a JGL Container. The add(), clear(), pushFront(), pushback(), popFront(), popBack(), and remove() methods work correctly, and are automatically converted into their JDK equivalents. The following example uses a VectorArray to sort and shuffle a JDK Vector.

// Copyright(c) 1996,1997 ObjectSpace, Inc.
import COM.objectspace.jgl.*;
import java.util.Vector;

public class Adapters2
  {
  public static void main( String[] args )
    {
    Vector vector = new Vector();
    vector.addElement( new Integer( 3 ) );
    vector.addElement( new Integer( -1 ) );
    vector.addElement( new Integer( 2 ) );
    vector.addElement( new Integer( -3 ) );
    vector.addElement( new Integer( 4 ) );

    VectorArray vectorArray = new VectorArray( vector );
    System.out.println( "Unsorted JDK Vector = " + vectorArray );

    Sorting.sort( vectorArray );
    System.out.println( "Sorted = " + vectorArray );

    Shuffling.randomShuffle( vectorArray );
    System.out.println( "Randomized = " + vectorArray );

    System.out.println( "JDK vector = " + vector );
    }
  }

Output

Unsorted JDK Vector = [3, -1, 2, -3, 4]
Sorted = [-3, -1, 2, 3, 4]
Randomized = [2, -1, 4, -3, 3]
JDK vector = [2, -1, 4, -3, 3]

Contents

Queues and Stacks

Algorithms