java.lang.NumberFormatException: 空字符串
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时间：2020-08-13 09:16:22 来源:igfitidea点击:
java.lang.NumberFormatException: empty String
提问by dragon40226
The code below keeps giving a java.lang.NumberFormatException: empty String:
下面的代码不断给出java.lang.NumberFormatException: empty String：
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
double AText = Double.parseDouble(angleAField.getText());
double BText = Double.parseDouble(angleBField.getText());
double CText = Double.parseDouble(angleCField.getText());
double aText = Double.parseDouble(sideaField.getText());
double bText = Double.parseDouble(sidebField.getText());
double cText = Double.parseDouble(sidecField.getText());
if (getMissing(angleAField.getText()) == false && getMissing(angleCField.getText()) == false) { //doesnt have angle C ,find Angle A
double angleA = Math.round(Math.asin((Math.sin(BText) / bText) * aText));
angleAField.setText("" + angleA);
}
}
public boolean getMissing(String Field) {
try {
if (Field.equals("")) {
return false; // has number
}
} catch (NumberFormatException e) {}
return true;
}
Error:
错误：
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1011)
at java.lang.Double.parseDouble(Double.java:540)
at sowhatstrig.trigFrame.jButton4ActionPerformed(trigFrame.java:520)
at sowhatstrig.trigFrame.access0(trigFrame.java:20)
at sowhatstrig.trigFrame.actionPerformed(trigFrame.java:353)
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:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
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:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access0(EventQueue.java:103)
at java.awt.EventQueue.run(EventQueue.java:682)
at java.awt.EventQueue.run(EventQueue.java:680)
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:696)
at java.awt.EventQueue.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
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)
采纳答案by hqt
You should check your field before parse double:
您应该在解析双精度之前检查您的字段：
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
double AText = ParseDouble(angleAField.getText());
double BText = ParseDouble(angleBField.getText());
double CText = ParseDouble(angleCField.getText());
double aText = ParseDouble(sideaField.getText());
double bText = ParseDouble(sidebField.getText());
double cText = ParseDouble(sidecField.getText());
// other code here same
}
double ParseDouble(String strNumber) {
if (strNumber != null && strNumber.length() > 0) {
try {
return Double.parseDouble(strNumber);
} catch(Exception e) {
return -1; // or some value to mark this field is wrong. or make a function validates field first ...
}
}
else return 0;
}
回答by Diogo Rocha
The string you're trying to parse as double is empty. You need to check if the getText() method returns a non empty string before trying to do the parsing cause you can't parse to double an empty string.
您尝试解析为 double 的字符串为空。在尝试进行解析之前，您需要检查 getText() 方法是否返回非空字符串，因为您无法将空字符串解析为双倍。
