Code:

package some.some.projectname;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import javax.microedition.khronos.opengles.GL10;


public class Rectangle
{
    private FloatBuffer vertexBuffer = null;
    private ShortBuffer indicesBuffer = null;
    private FloatBuffer colorBuffer = null;
    
    private int numOfIndices = 0;
    
    private float vertexList[] =
    {
        -1.0f, -1.0f, 0.0f,
        1.0f, -1.0f, 0.0f,
        1.0f, 1.0f, 0.0f,
        -1.0f, -1.0f, 0.0f
    };
    
    private short indexList[] =
    {
        0, 1, 2, 0, 2, 3
    };
    
    private float colorList[] =
    {
        1.0f, 0.0f, 0.0f, 1.0f,
        1.0f, 1.0f, 0.0f, 1.0f,
        0.0f, 1.0f, 0.0f, 1.0f
    };
    
    public Rectangle()
    {
        // Set vertex buffer
        ByteBuffer vbb = ByteBuffer.allocateDirect(vertexList.length * 4);
        vbb.order(ByteOrder.nativeOrder());
        vertexBuffer = vbb.asFloatBuffer();
        vertexBuffer.put(vertexList);
        vertexBuffer.position(0);
        
        // Set indices buffer
        numOfIndices = indexList.length;
        ByteBuffer tbibb = ByteBuffer.allocateDirect(numOfIndices * 2);
        tbibb.order(ByteOrder.nativeOrder());
        indicesBuffer = tbibb.asShortBuffer();
        indicesBuffer.put(indexList);
        indicesBuffer.position(0);
        
        // Set color buffer
        ByteBuffer cbb = ByteBuffer.allocateDirect(colorList.length * 4);
        cbb.order(ByteOrder.nativeOrder());
        colorBuffer = cbb.asFloatBuffer();
        colorBuffer.put(colorList);
        colorBuffer.position(0);
    }
    
    public void draw(GL10 gl)
    {
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
        
        gl.glColorPointer(4, GL10.GL_FLOAT, 0, this.colorBuffer);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, this.vertexBuffer);
        
        // Draw the Rectangle
        gl.glDrawElements(GL10.GL_TRIANGLES, this.numOfIndices,
                GL10.GL_UNSIGNED_SHORT, this.indicesBuffer);
        
        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glDisableClientState(GL10.GL_COLOR_ARRAY);
    }
}