java.lang.NumberFormatException对于输入字符串值是字母

Question

这是代码，当我输入一个字母它不会显示行.matches相反，我得到一个错误，但如果我删除了parseFloat rec1并删除其他if（ rec1 < total）那么.matches行会显示请帮助我如何提前谢谢

CashType c = new CashType（）; c.setVisible（true）;

c.jButton1.addActionListener(new java.awt.event.ActionListener() { 

     public void actionPerformed(java.awt.event.ActionEvent evt) { 
     String receive = c.jTextField1.getText(); 


     float total = total("sellno"+SellNoCount.getText()); 
     float rec1 = Float.parseFloat(receive); //this is line 1525 

      if(!receive.matches("[0-9]+")){ 
       JOptionPane.showMessageDialog(null,"Enter a Valid Amount"); 
       c.jTextField1.setText(""); 

      } 

      else if(receive.equalsIgnoreCase("")){ 
       JOptionPane.showMessageDialog(null,"Enter Amount"); 
      } 
      else if(rec1 < total){ 

       JOptionPane.showMessageDialog(null,"Insufficient Amount"); 

      } 

//错误

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "asdasd" 
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043) 
at sun.misc.FloatingDecimal.parseFloat(FloatingDecimal.java:122) 
at java.lang.Float.parseFloat(Float.java:451) 
at projectfinal.SellPage$32.actionPerformed(SellPage.java:1525) 

Answer 1

从错误信息，它看起来就像你正在进入 “asdasd” 到jTextField1。你试图解析这个值来浮动。如果字符串不是数字，Float.parseFloat(string)将抛出NumberFormatException。在parseFloat()方法中，字符串参数将被转换为基本浮点值。

您可以检查输入的值是否为数字，然后将其解析为浮点数。

float rec1 = 0; 

    if(isNumeric(receive)){ 
     rec1 = Float.parseFloat(receive); 
     if(rec1 < total){ 

     JOptionPane.showMessageDialog(null,"Insufficient Amount"); 

     } 
    }else { 
      JOptionPane.showMessageDialog(null,"Enter a Valid Amount"); 
      c.jTextField1.setText(""); 
     } 

的方法是

public static boolean isNumeric(String s) { 
    return s.matches("[-+]?\\d*\\.?\\d+"); 
}