学校的教学方法、教学组织形式、教学设备与社会生产力的发展无关。
参考答案:错
硝化甘油炸药适用于浅孔爆破和水下爆破。
本题中定义了一个简单的计算器,可以进行基本的四则运算。程序中包含16个按钮用来表示0~9、+、-、*、/、=运算符和小数点,程序顶部的文本框用来显示操作数以及结果。 import java. awt. * ; import java. awt. event. * ; import javax. swing. * ; public class java2 public static void main(String[] args) try UIManager. setLookAndFeel(UIManager. getSystemLookAndFeelClassName()); catch (Exception e) JFrame frame=new CalculatorFrame(); frame. show(); class CalculatorPanel extends JPanel implements ActionListener private JTextField display; private JButton btn; private double arg=0; private String op="= "; private boolean start=true; public CalculatorPanel() setLayout(new BorderLayout()); dispIay=new JTextField("0"); display, setEditable(false); add(display, "North"); JPanel p=new JPanel(); p. setLayout(new GridLayout(4,4)); String buttons="789/456*123-0.=+"; for (int i=0; i<buttons, length(); i++) btn=new JButton(buttons. substring(i, i+1)); p. add(btn); ______; add(p, "Center"); public void actionPerformed(ActionEvent evt) String s=evt. getActionCommand(); if(’0’<=s. charAt(0) && s. charAt(0)<=’9’ || s. equals(".")) if (start) display. setText(s); else display, setText(display, getText()+s); start=false; else if (start) if (s. equals("-")) display. setText(s); start=false; else op=s; else double x=______; calculate(x); op=s; start=true; public void calculate(double n) if (op. equals("+")) arg+=n; else if (op. equals("-")) arg-= n; else if (op. equals("*")) arg *=n; else if (op. equals("/")) arg /=n; else if (op. equals("=")) arg=n; display, setText(""+arg); class CalculatorFrame extends JFrame public CalculatorFrame() setTitle("java2"); setSize(220,180); addWindowListener(new WindowAdapter() public void windowClosing(WindowEvent e) System. exit(0); ); Container contentPane=getContentPane(); contentPane, add(new CalculatorPanel());