public class CustomCalculator extends Frame implements ActionListener{
Panel jp1 = new Panel();
Panel jp2 = new Panel();
Panel jp3 = new Panel();
Panel jp4 = new Panel();
Panel jp5 = new Panel();
Panel center_merge = new Panel();
Label l2 = new Label("Quantity : ");
TextField l2a = new TextField(20);
Label l3 = new Label("Invoice Value : ");
TextField l3a = new TextField(20);
Label l4 = new Label("Exchange Rate : ");
TextField l4a = new TextField(20);
Label l5 = new Label("Costing(A) : ");
TextField l5a = new TextField();
Label l6 = new Label("(A + 1%)(B) : ");
Label l6a = new Label();
Label l7 = new Label("BCD (C) : ");
Label l7a = new Label("");
Label l8 = new Label("CVD (D) : ");
Label l8a = new Label("");
Label l9 = new Label("Custom Education Cess (E) : ");
Label l9a = new Label("");
Label l10 = new Label("Custom Sec & Higher Edu.Cess (F) : ");
Label l10a = new Label("");
Label l11 = new Label("Additional Duty Imports (G) : ");
Label l11a = new Label("");
Label l12 = new Label("Total (H) : ");
Label l12a = new Label("");
Label l13 = new Label("Costing+Total (I) : ");
Label l13a = new Label("");
Label l14 = new Label("(H/Quantity) (J) : ");
Label l14a = new Label("");
Label l15 = new Label("4% SAD (G/Quantity) (K) : ");
Label l15a = new Label("");
Label l16 = new Label("Net Costing (L) : ");
Label l16a = new Label("");
Label l17 = new Label("Transportation (M) : ");
TextField l17a = new TextField(5);
Label l18 = new Label("Godown Rate (N) : ");
TextField l18a = new TextField(5);
Label l19 = new Label("Brokerage (O) : ");
TextField l19a = new TextField(5);
Label l20 = new Label("Actual Costing (P) : ");
Label l20a = new Label("");
Label l21 = new Label("Small Gatepass (Q) : ");
Label l21a = new Label("");
Label l22 = new Label("Big Gatepass (R) : ");
Label l22a = new Label("");
Button l2b = new Button("reset");
Button l3b = new Button("reset");
Button l4b = new Button("reset");
Button master_reset = new Button("reset all");
Button calc = new Button("Calculate");
public CustomCalculator()
{
super("Custom Calculator");
this.setSize(800,700);
jp1.setLayout(new FlowLayout());
//jp1.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp1.add(l2);
jp1.add(l2a);
jp1.add(l2b);
jp1.add(l3);
jp1.add(l3a);
jp1.add(l3b);
jp1.add(l4);
jp1.add(l4a);
jp1.add(l4b);
jp2.setLayout(new GridLayout(6,2));
//jp2.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp2.add(l5);
jp2.add(l5a);
jp2.add(l6);
jp2.add(l6a);
jp2.add(l7);
jp2.add(l7a);
jp2.add(l8);
jp2.add(l8a);
jp2.add(l9);
jp2.add(l9a);
jp2.add(l10);
jp2.add(l10a);
jp3.setLayout(new GridLayout(6,2));
//jp3.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp3.add(l11);
jp3.add(l11a);
jp3.add(l12);
jp3.add(l12a);
jp3.add(l13);
jp3.add(l13a);
jp3.add(l14);
jp3.add(l14a);
jp3.add(l15);
jp3.add(l15a);
jp3.add(l16);
jp3.add(l16a);
jp4.setLayout(new GridLayout(6,2));
//jp4.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp4.add(l17);
jp4.add(l17a);
jp4.add(l18);
jp4.add(l18a);
jp4.add(l19);
jp4.add(l19a);
jp4.add(l20);
jp4.add(l20a);
jp4.add(l21);
jp4.add(l21a);
jp4.add(l22);
jp4.add(l22a);
center_merge.setLayout(new GridLayout(1,3));
//center_merge.setBorder(BorderFactory.createLineBorder(Color.GRAY));
center_merge.add(jp2);
center_merge.add(jp3);
center_merge.add(jp4);
jp5.setLayout(new FlowLayout());
//jp5.setBorder(BorderFactory.createLineBorder(Color.GRAY));
jp5.add(calc);
jp5.add(master_reset);
this.setLayout(new BorderLayout());
this.add(jp1,BorderLayout.NORTH);
this.add(center_merge,BorderLayout.CENTER);
this.add(jp5,BorderLayout.SOUTH);
this.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent we)
{
System.exit(0);
}
});
l2b.addActionListener(this);
l3b.addActionListener(this);
l4b.addActionListener(this);
calc.addActionListener(this);
master_reset.addActionListener(this);
this.setVisible(true);
}
public static void main(String[] args) {
new CustomCalculator();
}
@Override
public void actionPerformed(ActionEvent ae) {
double quantity = 0;
double invoice_value = 0;
double exchange_rate = 0;
double A=0;
double B=0;
double C=0;
double D=0;
double E=0;
double F=0;
double G=0;
double H=0;
double I=0;
double J=0;
double K=0;
double L=0;
double M = 0;
double N = 0;
double O=0;
double P=0;
double Q=0;
double R=0;
try
{
quantity = Double.parseDouble(l2a.getText());
invoice_value = Double.parseDouble(l3a.getText());
exchange_rate = Double.parseDouble(l4a.getText());
M = Double.parseDouble(l17a.getText());
N = Double.parseDouble(l18a.getText());
O = Double.parseDouble(l19a.getText());
A = invoice_value*exchange_rate;
B = A+(0.01*A);
C = 0.075*B;
D = 0.12*(B+C);
E = 0.02*(C+D);
F = 0.01*(C+D);
G = 0.04*(B+C+D+E+F);
H = C+D+E+F+G;
I = A+H;
J = H/quantity;
K = G/quantity;
L = J-K;
P = L+M+N+O;
Q = (0.12*B)/quantity;
R = Q+K;
if(ae.getActionCommand().equals("calc"))
{
l5a.setText(String.valueOf(A));
l6a.setText(String.valueOf(B));
l7a.setText(String.valueOf(C));
l8a.setText(String.valueOf(D));
l9a.setText(String.valueOf(E));
l10a.setText(String.valueOf(F));
l11a.setText(String.valueOf(G));
l12a.setText(String.valueOf(H));
l13a.setText(String.valueOf(I));
l14a.setText(String.valueOf(J));
l15a.setText(String.valueOf(K));
l16a.setText(String.valueOf(L));
l20a.setText(String.valueOf(P));
l21a.setText(String.valueOf(Q));
l22a.setText(String.valueOf(R));
}
else if(ae.getActionCommand().equals("master_reset"))
{
l5a.setText("");
l2a.setText("");
l3a.setText("");
l4a.setText("");
}
}
catch (Exception ex)
{
l5a.setText(ex.toString());
// l3a.setText(ex.toString());
}
}
}
单击“计算”按钮（“计算按钮”）后，计算出的值未出现在相应的标签中，并显示一个异常，表示
java.lang.NumberFormatException: Empty string。我不知道解决方案。请帮忙。 最佳答案
该行exchange_rate = Double.parseDouble（l4a.getText（））;给您这个例外，因为l4a中没有值，并且您试图将其解析为双精度值，
尝试在catch子句中打印异常。