錯誤掃描文本文件時顯示錯誤“線程“ AWT-EventQueue-0”中的異常java.util.NoSuchElementException”

Question

public class checkDuplicateNames1 {



public boolean checkDuplicateNames1(String name , String surname){
   boolean found = false;
    File file = new File("transactions.txt");

    try {
        Scanner sc = new Scanner(new File("transactions.txt"));
        sc.useDelimiter("/");


        while(sc.hasNext()){

        String userName = sc.next();
        String userLastName = sc.next();
        String userCash = sc.next();
        String paidStatus = sc.next();

        if((userName.equals(name)&&userLastName.equals(surname))){

            found = true;

        }
        else
        {

            found = false;
        }
        }

    } catch (FileNotFoundException ex) {
        Logger.getLogger(checkDuplicateNames.class.getName()).log(Level.SEVERE, null, ex);
    }






 return found;



}

}

當我使用“ boolean checkDuplicateNames1”方法時，出現此錯誤

Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1371)
at Lending.checkDuplicateNames1.checkDuplicateNames1(checkDuplicateNames1.java:41)
at Lending.Loan.jButton1ActionPerformed(Loan.java:250)
at Lending.Loan.access$200(Loan.java:24)
at Lending.Loan$3.actionPerformed(Loan.java:137)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)  

我試圖使用像bufferedReader這樣的不同文件讀取器，它是相同的，

這是使用“ checDuplicateNames1”方法的“貸款類”方法

 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    // TODO add your handling code here:


    String name = jTextField1.getText();
    String surname = jTextField4.getText();
    String cash = jTextField5.getText();
    System.out.println("loan clicked");

    try {

        String info = name + "/" + surname + "/" + cash + "/" + "unpaid";

        checkDuplicateNames1 c = new checkDuplicateNames1();
        boolean duplicated = c.checkDuplicateNames1(name,surname);

        if(duplicated == true){
            System.out.println("duplicated");
            this.currentName = name;
            this.currentSurname = surname;
          JOptionPane.showMessageDialog(null,"Person already in the Record ");
          wannaAddLoanValue w = new wannaAddLoanValue(name,surname,cash);
          w.show();



        }
        else
        {
            File file = new File("transactions.txt");
             PrintWriter writer = new PrintWriter(new FileWriter(file,true));
             String info1 = name + "/" + surname + "/" + cash + "/" + "unpaid";
             writer.println(info1); 
              writer.close();

        }



    } catch (FileNotFoundException ex) {
        Logger.getLogger(Loan.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(Loan.class.getName()).log(Level.SEVERE, null, ex);
    }




}                                

並且文件中的文本也像這樣

rodchris/toledo/200/unpaid
yannie/taub/890/unpaid

Answer 1

你應該總是調用sc.hasNext()之前sc.next(); 。

while(sc.hasNext()){

    // This line is OK
    String userName = sc.next();

    // The following lines can cause NoSuchElementException
    String userLastName = sc.next();
    String userCash = sc.next();
    String paidStatus = sc.next();

checkDuplicateNames1()可以按以下方式重構：

public boolean checkDuplicateNames1(String name, String surname) {
    boolean found = false;
    try (Scanner sc = new Scanner(new File("transactions.txt"))) {
        sc.useDelimiter("/");
        String userName = sc.hasNext() ? sc.next() : null;
        String userLastName = sc.hasNext() ? sc.next() : null;
        return userName != null && userLastName != null && userName.equals(name) && userLastName.equals(surname);            
    } catch (FileNotFoundException ex) {
        Logger.getLogger(checkDuplicateNames.class.getName()).log(Level.SEVERE, null, ex);
    }
    return found;
}

Answer 2

你班上哪一行是41 ？ 即哪個next()導致錯誤，

我認為hasNext()認為，當前整個輸入為1個令牌，但是當你調用next()幾次，你只拿到了第一個1個例外，要解決這個問題，我認為你必須檢查hasNext()前各next()

while(sc.hasNext()){
    String userName="",userLastName="",userCash="",paidStatus="";

    //first one already checked in while(...)
    userName = sc.next();

    if(sc.hasNext())        
        userLastName = sc.next();

    if(sc.hasNext())
        userCash = sc.next();

    if(sc.hasNext())
        paidStatus = sc.next();

    //... rest of code

在其余的代碼中，您可能需要檢查每個變量是否為空

if(!userLastName.isEmpty()) ...