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来自textfield的Java int(Java int from textfield)

 我是Java新手。 我试图从JavaFX中的计算器的文本字段中获取int。 我有2个文本框可供人们编写一个数字：  
hb.getChildren().addAll(label1, textField);
textField.getText();
hb.setSpacing(10);
hb.getChildren().addAll(label2, textField2);
textField2.getText();
hb.setSpacing(10);
 
 所以这就是我从文本字段获取int的方法，但它不起作用：  
int x = Integer.parseInt(textField.getText());
int y = Integer.parseInt(textField2.getText());
 
 有谁知道我做错了什么？ 我在互联网上看到人们使用了事件，但我不确定在这种情况下是否必须使用它。  
 错误日志：  
 Exception in Application start method
 java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
 Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
 Caused by: java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:592)
    at java.lang.Integer.parseInt(Integer.java:615)
    at test.start(test.java:57)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    ... 1 more Exception running application test
 
 我希望有一个人可以帮助我，  
 托马斯 

I'm new to Java. I'm trying to get an int from a textfield for my calculator in JavaFX. I have 2 textfields where people can write a number: 
hb.getChildren().addAll(label1, textField);
textField.getText();
hb.setSpacing(10);
hb.getChildren().addAll(label2, textField2);
textField2.getText();
hb.setSpacing(10);
 
So this is what I made to get an int from a textfield but it doesnt work: 
int x = Integer.parseInt(textField.getText());
int y = Integer.parseInt(textField2.getText());
 
Does anyone know what I'm doing wrong? I saw on internet people used event but I'm not sure if in this case I have to use it.  
Error log: 
 Exception in Application start method
 java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
 Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
 Caused by: java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:592)
    at java.lang.Integer.parseInt(Integer.java:615)
    at test.start(test.java:57)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    ... 1 more Exception running application test
 
I hope someone can help me, 
Thomas

原文：https://stackoverflow.com/questions/49937561

更新时间：2021-12-20 13:12

最满意答案

 是的，这是一个非常基本的单身人士。 它做它应该做的事情，没有特别的装饰。  
 你在互联网上找到的例子通常描述一个懒惰的初始化单例，强调getInstance()的性能（即避免同步，不允许在多个线程同时调用getInstance()时创建多个实例）。  
 如果您不需要延迟初始化，那么创建单例变得非常简单，就像您在Runtime看到的一样。  
 最后，你可以找到很多关于单例模式的东西（其中一些是误导性的），但它并不真正保证它。 这并不是那么有趣，有些人认为它是一种反模式，如果你发现自己编写自己的单例很多，你可能做的不太对劲。  
 最后，如果你确实认为你需要一个懒惰的初始化单例，那么当前的标准实现是enum 。  
public enum MySingleton {
    INSTANCE

    public String getSarcasticMessage() {
        return "I'm a lazy loaded singleton, use me for everything!";
    }
}

MySingleton.INSTANCE.getSarcasticMessage();  // This is how to use it

Yes, that's a very basic singleton. It does what it's supposed to do with no special frills. 
The examples you find on the internet usually describe a lazy initialized singleton with emphasis on the performance of getInstance() (i.e. avoid synchronized, don't allow creating multiple instances if multiple threads call getInstance() at the same time and so forth). 
If you don't need lazy initialization it becomes very simple to create a singleton, as you can see with Runtime. 
Finally, you can find a lot of things written about the singleton pattern (some of them misleading), but it doesn't really warrant it. It's not that interesting, some consider it an anti-pattern, and if you find yourself writing your own singletons a lot, you're probably doing something not quite right. 
Extra finally, if you do think you need a lazily initialized singleton, the current standard implementation is with enum. 
public enum MySingleton {
    INSTANCE

    public String getSarcasticMessage() {
        return "I'm a lazy loaded singleton, use me for everything!";
    }
}

MySingleton.INSTANCE.getSarcasticMessage();  // This is how to use it

来自textfield的Java int(Java int from textfield)

最满意答案

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