Here you can find the source of setPreferredSize(JComponent comp, int height, int width)
public static Dimension setPreferredSize(JComponent comp, int height, int width)
//package com.java2s; /*// www .ja va2 s.c om Strandz LGPL - an API that matches the user to the data. Copyright (C) 2007 Chris Murphy Strandz LGPL is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA The authors can be contacted via www.strandz.org */ import javax.swing.JComponent; import java.awt.*; public class Main { public static final int LEAVE = -999; public static Dimension setPreferredSize(JComponent comp, int height, int width) { Dimension result = null; Dimension preferredSize = comp.getPreferredSize(); // Err.pr( "preferred size was " + preferredSize); if (height != LEAVE) preferredSize.height = height; if (width != LEAVE) preferredSize.width = width; comp.setPreferredSize(preferredSize); result = preferredSize; return result; } }