编译完上述程序后解释输出 [英] Explain the output after compiling the above program

问题描述

import java.util.*;
public class Input {

	public static void main(String[] args) {
		Scanner s=new Scanner(System.in);
		System.out.println("Enter something");
		int a=s.nextInt();
		System.out.println("The thing entered is:"+a);
		Scanner w=new Scanner(System.in);
		System.out.println("Now enter a string");
		String q=s.nextLine();
		System.out.println("The entered String is:"+q);
		
	}

}

我的尝试：



我的输出是：

输入内容

54

输入的东西是：54

现在输入一个字符串

输入的字符串是：

**它再也不需要输入

What I have tried:

My output is:
Enter something
54
The thing entered is:54
Now enter a string
The entered String is:
**it never takes the input again

推荐答案

因为输入缓冲区中已有一个行结束字符等待读取（数字54后面的字符）。因此，您对 nextLine 的以下调用将读取该内容，然后终止。在读取令牌而不是完整的行之后，您需要耗尽输入缓冲区。你也不需要多个扫描仪对象，一个就足够了。

Because there is already a line end character in the input buffer waiting to be read (the character(s) following the number 54). So your following call to nextLine will read that and then terminate. You need to drain your input buffers after reading tokens rather than complete lines. You also do not need multiple scanner objects, one will be enough.

仔细阅读你的代码：

Read very carefully your code:

import java.util.*;
public class Input {

    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        System.out.println("Enter something");
        int a=s.nextInt();
        System.out.println("The thing entered is:"+a);
        Scanner w=new Scanner(System.in); // Why this, but still read s ?
        System.out.println("Now enter a string");
        String q=s.nextLine();
        System.out.println("The entered String is:"+q);
    }
}

你的代码没有你想象的那样，或者你不明白为什么！



有一个几乎通用的解决方案：逐步在调试器上运行代码，检查变量。

调试器在这里显示你的代码正在做什么和你的任务是与它应该做的比较。

调试器中没有魔法，它不知道你的代码应该做什么，它没有找到bug，它只是帮助你通过向您展示正在发生的事情。当代码没有达到预期的效果时，你就接近了一个错误。

要查看你的代码在做什么：只需设置断点并查看代码是否正常运行，调试器允许你执行第1行第1行，并在执行时检查变量。



调试器 - 维基百科，免费的百科全书 [ ^ ]


掌握调试Visual Studio 2010 - 初学者指南 [ ^ ]

使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]



http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html [ ^ ]

https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html [ ^ ]



这里的调试器只显示你的代码正在做什么，你的任务是与它应该做什么进行比较。

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.

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