java - ファイル名の後に .txt を書き込むと、nullpointerexception が発生します

Question

ファイル名の後に .txt を書き込むたびに、nullpointreexception エラーが発生します。しかし、.txt を書き込まないと、プログラムは実行されているように見えますが、システムが指定されたファイルを見つけることができないと常に表示されます。どうすればいいのかわかりません。私を案内してください。これは私のコードです

public void signin(){
    //System.out.println(System.getProperty("user.dir"));
    File file=new File("C:\\Workplace\\3rdLastLab\\file1.txt");
    try{
        FileReader fr=new FileReader(file);
        BufferedReader br=new BufferedReader(fr);
        Scanner sc=new Scanner(br);
        String text1=field1.getText();
        String text2=field2.getText();
        String text3=text1+"."+text2;


        while(sc.hasNext()){

            String string= sc.next();   
            if(text3.equals(string)==true){
                JOptionPane.showMessageDialog(null, "You are logged in!");
            }
            else
                JOptionPane.showMessageDialog(null, "Wrong user name or password");
        }

        br.close();
    }
    catch (IOException e){
        JOptionPane.showMessageDialog(null, e.getMessage());
    }

}

そして、私はこれらのエラーを受け取ります

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Login.signin(Login.java:36)
at Login.actionPerformed(Login.java:122)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)