addsubstractoperation.java

简单的计算器程序

package calculate.operations;

import calculate.Calculate;
import calculate.Operation;

public class AddSubstractOperation implements Operation {

	public void execute(Calculate calculate) {
		String showText = calculate.getShowText();

		if (showText.startsWith("-")) {
			calculate.setShowText(showText.substring(1));
		} else {
			calculate.setShowText("-" + showText);
		}
	}

}