Sync Issue - Controller.java

import java.util.HashMap;
import java.util.Map;

public class Controller{
    Tuple3f defaultColor = new Tuple3f();
    Map<Tuple3f, TestBuffer> colorToBufferMap = new HashMap<Tuple3f, TestBuffer>();
    int i=0;

    public void addSome(Integer toAdd) {
        TestBuffer buffer = getBuffer();

        for (int j=0;j<toAdd;j++) {
            buffer.add(i++);
        }
    }

    public void remove() {
        TestBuffer oldBuffer = getBuffer();
        oldBuffer.remove(i++);
    }

    public TestBuffer getBuffer() {
        TestBuffer buffer = null;
        if (colorToBufferMap.containsKey(defaultColor)) {
            buffer = colorToBufferMap.get(defaultColor);
        } else {
            buffer = new TestBuffer();
            colorToBufferMap.put(defaultColor, buffer);
        }
        return buffer;
    }
}