VBO MapBuffer problem

Hi! I use JOGL 1.1.1.a. I can draw my cube using vbo but when I want to animate the cube I have a problem with change vertices position.

Init VBO

gl.glGenBuffers(bufferSize, IntBuffer.wrap(buffer));

verticesID = buffer[0];
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, verticesID);
gl.glBufferData(GL.GL_ARRAY_BUFFER, BufferUtil.SIZEOF_FLOAT * vertices.capacity(), vertices, GL.GL_DYNAMIC_DRAW);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, 0);

normalsID = buffer[1];
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, normalsID);
gl.glBufferData(GL.GL_ARRAY_BUFFER, BufferUtil.SIZEOF_FLOAT * normals.capacity(), normals, GL.GL_DYNAMIC_DRAW);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, 0);

gl.glEnableClientState(GL.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL.GL_NORMAL_ARRAY);




Display and Update Vertices

gl.glPushMatrix();

gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_AMBIENT, material.getAmbient(), 0);
gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_DIFFUSE, material.getDiffuse(), 0);
gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_SPECULAR, material.getSpecular(), 0);
gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_EMISSION, material.getEmission(), 0);
gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_SHININESS, material.getShininess(), 0);

gl.glBindBuffer(GL.GL_ARRAY_BUFFER, verticesID);
gl.glVertexPointer(3, GL.GL_FLOAT, 0, 0);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, 0);

gl.glBindBuffer(GL.GL_ARRAY_BUFFER, normalsID);
gl.glNormalPointer(GL.GL_FLOAT, 0, 0);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, 0);

gl.glDrawArrays(GL.GL_QUADS, 0, 24);

gl.glBindBuffer(GL.GL_ARRAY_BUFFER, verticesID);

byteBuffer = gl.glMapBuffer(GL.GL_ARRAY_BUFFER, GL.GL_READ_WRITE);
if(bufferRW != null)
{
     srcVertices = byteBuffer.asFloatBuffer();
     
     vertices.rewind();
           
     for(int i = 0; i < 24; i++)
     {
          vX = srcVertices.get();
          vY = srcVertices.get();
          vZ = srcVertices.get();

          vertices.put(vX);
          vertices.put(vY + 0.2f);
          vertices.put(vZ);
     }
}
gl.glUnmapBuffer(GL.GL_ARRAY_BUFFER);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, 0);
gl.glPopMatrix();



The cube should move up but nothing happens. What is wrong with my code ?

Solved:

srcVertices = byteBuffer.asFloatBuffer();
srcVertices.rewind();                    
                                           
for(int i = 0; i < 24; i++)              
{                                                                            
    vX = srcVertices.get(i * 3);        
    vY = srcVertices.get(i * 3 + 1);    
    vZ = srcVertices.get(i * 3 + 2);    
                                           
    srcVertices.put(i * 3, vX);          
    srcVertices.put(i * 3 + 1, vY + 0.5f);
    srcVertices.put(i * 3 + 2, vZ);                                      
}