线程 "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException 中的异常：字符串索引超出范围：8

Question

我的 jPanel 上有几个 jComboBoxes 和 jTextFields。

选择并键入的值保存在文本文件中。

PrintWriter outfile = new PrintWriter(new BufferedWriter(new FileWriter...
outfile.write(jcb1.getSelectedItem().toString().substring(1, 8));
outfile.write(jTextField1.getText());

但是当我允许 jComboBoxes 为空时，我无法保存 jcb1 的空值并出现此错误：

Exception in thread "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException: String index out of range: 8
    at java.lang.String.substring(String.java:1907)
    at main.panel.saveActionPerformed(panel.java:5929)
    at main.panel.access0(panel.java:36)
    at main.panel.actionPerformed(panel.java:5713)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    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:6516)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
    at java.awt.Component.processEvent(Component.java:6281)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4872)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4698)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4698)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access0(EventQueue.java:103)
    at java.awt.EventQueue.run(EventQueue.java:694)
    at java.awt.EventQueue.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue.run(EventQueue.java:708)
    at java.awt.EventQueue.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

我想保存 jComboBox 的空值，但由于 substring 出现错误。我不知道如何避免这个问题。任何帮助将不胜感激。

Answer 1

在获取子字符串之前，检查字符串长度。

String test = "test12";
String subtest;
//long version
if(test.length() > 8){
      subtest = test.substring(1, 8);
} else {
      subtest = test.substring(1, test.length());
}
//short version
subtest = test.substring(1, test.length() > 8 ? 8 : test.length());
System.out.println(subtest); //Output: est12

线程 "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException 中的异常：字符串索引超出范围：8

Exception in thread "AWT-EventQueue-0" java.lang.StringIndexOutOfBoundsException: String index out of range: 8

java

swing

substring

jcombobox

bufferedwriter