我是java语言的新手，我试图在google的帮助下制作一个程序，这是一个applet程序但是即使eclipse中没有错误它也不会运行。如果它可以在applet中使用，我也对cardLayout感到困惑，所以我很感激你的帮助。
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.io.*;
import javax.swing.*;
public class Proto extends Applet implements ActionListener {
Label Store = new Label("WELCOME TO SCHOOL SUPPLIES STORE");
double Price, Subtotal;
String Code;
String ITname;
String quan;
String choice;
int qty;
double Total;
CardLayout card1;
Container c, d;
File writer;
Button buttonBUY = new Button ("BUY");
Button buttonCONFIRM = new Button("Confirm");
Button buttonCONFIRM1 = new Button("Confirm your transaction?");
Button back = new Button ("Back");
Button close = new Button ("Close");
Font StoreFont = new Font("Times New Roman", Font.BOLD, 15);
Label flb1 = new Label ("Item");
Label flb2 = new Label ("Quantity");
Label flb3 = new Label ("Price");
Label flb4 = new Label ("SUbtotal");
Label lb1 = new Label("ITEM CODE ");
Label lb2 = new Label(" PRODUCT NAME ");
Label lb3 = new Label(" PRICE ");
Label lb4 = new Label (" QUANTITY ");
Label c1 = new Label ("HBW01");
Label HBW01pn = new Label (" HBW Ballpen ");
Label HBW01p = new Label (" 8.00PHP ");
Label c2 = new Label ("MNG02");
Label MNG02pn = new Label (" Mongol Pencil ");
Label MNG02p = new Label (" 6.00PHP ");
Label c3 = new Label ("MRK03");
Label MRK03pn = new Label (" Marker/Pentel ");
Label MRK03p = new Label (" 30.00PHP ");
Label c4 = new Label ("YLW04");
Label YLW04pn = new Label (" One Whole Yellow Pad ");
Label YLW04p = new Label (" 30.00PHP ");
Label c5 = new Label ("CRT05");
Label CRT05pn = new Label (" Cartolina ");
Label CRT05p = new Label (" 10.00PHP ");
Label c6 = new Label ("MNL06");
Label MNL06pn = new Label (" Manila Paper ");
Label MNL06p = new Label (" 6.00PHP ");
Label c7 = new Label ("EGL07");
Label EGL07pn = new Label (" Elmer's Glue ");
Label EGL07p = new Label (" 12.00PHP ");
Label c8 = new Label ("CPR08");
Label CPR08pn = new Label (" Colored Paper ");
Label CPR08p = new Label (" 1.00PHP ");
Label c9 = new Label ("BPR09");
Label BPR09pn = new Label (" Bond Paper ");
Label BPR09p = new Label (" 1.00PHP ");
Label c10 = new Label ("OPR10");
Label OPR10pn = new Label (" Oslo Paper ");
Label OPR10p = new Label (" 1.00PHP ");
Label c11 = new Label ("GPR11");
Label GPR11pn = new Label (" Graphing Paper ");
Label GPR11p = new Label (" 1.00PHP ");
Label c12 = new Label ("RLR12");
Label RLR12pn = new Label (" Ruler ");
Label RLR12p = new Label (" 10.00PHP ");
Label c13 = new Label ("PRT13");
Label PRT13pn = new Label (" Protractor ");
Label PRT13p = new Label (" 10.00PHP ");
Label c14 = new Label ("ERS14");
Label ERS14pn = new Label (" Eraser ");
Label ERS14p = new Label (" 5.00PHP ");
Label c15 = new Label ("FLR15");
Label FLR15pn = new Label (" Notebook Filler ");
Label FLR15p = new Label (" 15.00PHP ");
Label c16 = new Label ("SCR16");
Label SCR16pn = new Label (" Scissor ");
Label SCR16p = new Label (" 10.00PHP ");
TextArea TA = new TextArea (10, 10);
TextArea RP = new TextArea (10, 80);
TextArea CH = new TextArea (10, 10);
TextArea TOT = new TextArea (10, 10);
public void init() {
back.addActionListener(this);
buttonBUY.addActionListener(this);
buttonCONFIRM.addActionListener(this);
buttonCONFIRM1.addActionListener(this);
close.addActionListener(this);
card1 =new CardLayout(800,600);
c.setLayout(card1);
c.add(Store);
c.add(lb1);c.add(lb2);c.add(lb3);c.add(lb4);
c.add(c1);c.add(HBW01pn);c.add(HBW01p);
c.add(c2);c.add(MNG02pn);c.add(MNG02p);
c.add(c3);c.add(MRK03pn);c.add(MRK03p);
c.add(c4);c.add(YLW04pn);c.add(YLW04p);
c.add(c5);c.add(CRT05pn);c.add(CRT05p);
c.add(c6);c.add(MNL06pn);c.add(MNL06p);
c.add(c7);c.add(EGL07pn);c.add(EGL07p);
c.add(c8);c.add(CPR08pn);c.add(CPR08p);
c.add(c9);c.add(BPR09pn);c.add(BPR09p);
c.add(c10);c.add(OPR10pn);c.add(OPR10p);
c.add(c11);c.add(GPR11pn);c.add(GPR11p);
c.add(c12);c.add(RLR12pn);c.add(RLR12p);
c.add(c13);c.add(PRT13pn);c.add(PRT13p);
c.add(c14);c.add(ERS14pn);c.add(ERS14p);
c.add(c15);c.add(FLR15pn);c.add(FLR15p);
c.add(c16);c.add(SCR16pn);c.add(SCR16p);
c.add(buttonBUY);
} //end of init()
public void actionPerformed (ActionEvent ae) {
if (ae.getSource() == buttonBUY) {
second(c);
}
if (ae.getSource() == buttonCONFIRM)
if (Code=="HBW01"){
Price = 8.00;
ITname = "HBW Ballpen ";
}
else if (Code=="MNG02"){
Price = 6.00;
ITname = "Mongol Pencil ";
}
else if (Code=="MRK03"){
Price = 30.00;
ITname = "Marker";
}
else if (Code=="YLW04"){
Price = 30.00;
ITname = "Yellow Pad ";
}
else if (Code=="CRR05"){
Price = 10.00;
ITname = "Cartolina ";
}
else if (Code=="MNL06"){
Price = 6.00;
ITname = "Manila Paper";
}
else if (Code=="EGL07"){
Price = 12.00;
ITname = "Elmer’s Glue ";
}
else if (Code=="CPR08"){
Price = 1.00;
ITname = "Colored Paper ";
}
else if (Code=="BPR09"){
Price = 1.00;
ITname = "Bond Paper ";
}
else if (Code=="OPR10"){
Price = 1.00;
ITname = "Oslo Paper ";
}
else if (Code=="GPR11"){
Price = 1.00;
ITname = "Graphing Paper ";
}
else if (Code=="RLR12"){
Price = 10.00;
ITname = "Ruler";
}
else if (Code=="PTR13"){
Price = 10.00;
ITname = "Protractor";
}
else if (Code=="ERS14"){
Price = 5.00;
ITname = "Eraser ";
}
else if (Code=="FLR15"){
Price = 15.00;
ITname = "Notebook Filler ";
}
else if (Code=="SCR16"){
Price = 10.00;
ITname = "Scissor";
}
else{
error(d);
}
if (ae.getSource()== back){
second(c);
}
if (ae.getSource() == close){
System.exit(0);
}
}
public void second(Container d){
Label Enter = new Label("Enter Code");
d.add(Enter);
d.add(TA); d.add(buttonCONFIRM);
String Code = TA.getText();
third(d);
}
public void third(Container e){
Label Quantity = new Label("Enter Quantity");
e.add(Quantity);
quan = Quantity.getText();
qty = Integer.parseInt(quan);
Subtotal = Price * qty;
Total = Total + Subtotal;
e.add(buttonCONFIRM1);
}
public void error(Container f){
Label derror = new Label("Code Not Found");
f.add(derror);
f.add(back);
}
public void ask(Container g){
RP.append(flb1.getText() + "\t" + flb2.getText() + "\t" + flb3.getText() + "\t" + flb4.getText() + "\t TOTAL");
RP.append(ITname + "\t" + quan + "\t" + Price + "\t" + Subtotal);
Label eof = new Label("Would you like to have another transaction? [Y/N]" );
g.add(eof); g.add(CH);
choice = CH.getText();
if (choice == "Y"){
second(g);
}
else
last(g);
}
public void last(Container h){
Label T = new Label ("Total is:");
String Final = String.valueOf(Total);
TOT.append(Final);
h.add(RP);
h.add(T); h.add(TOT);
h.add(close);
}
}
答案 0 :(得分：0)
替换此行：
itertools.tee有了这个：
Container c, d;
因为您尝试将布局应用于具有空引用的未存在对象。
对于其余部分，applet会启动，但它会在控制台中打印异常。你应该留意它。