Owl Sams Teach Yourself Java 2 in 24 Hours

Hour 24: Making Your Knowledge Add Up


  • The first step in the development of a project like this should be to design the graphical user interface. The interface for the author's MiniCalc project can be found in MiniCalcGUI.java, MiniCalcGUI.class, CalcAppletGUI.java, CalcAppletGUI.class, and CalcAppletGUI.html.
  • One of the requirements of the project was that the equals key should be disabled when the program starts. This is handled by calling the setEnabled(false) method on that component.
  • The interface is created by using two different groups of components arranged using the GridLayout layout manager. The first is created with a call to the GridLayout(6, 1, 5, 5) constructor method. This creates a layout of six rows and only one column. The last two arguments are used to provide some horizontal and vertical space between each component in the grid. The graphic below shows where these six rows are located on the interface:
  • On each of these rows, another grid layout is used to arrange the components on that row. This layout manager is created with a call to the GridLayout(1, 4, 5, 5) constructor, which has one row, four columns, and a horizontal and vertical gap of 5 pixels each. The graphic below shows one of these rows, with black lines around each of the cells in the grid:
  • In a container organized by the GridLayout manager, the component you put into a cell will expand to fill all the space that's available to it.
  • If you have questions about developing a calculator interface, contact the author.


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