PrintWriter的混乱

Question

我有一个关于PrintWriter的Java中的问题，这里是我的代码：

import java.io.File; 
    import java.io.FileNotFoundException; 
    import java.io.PrintWriter; 
    import java.util.Scanner; 


public class Out { 

public static void main(String[] args) { 

    try{ 
File a=new File("C:/Users/Acer/Desktop/abc.txt"); 
PrintWriter out=new PrintWriter(a); 
Scanner c=new Scanner(System.in); 


while(c.hasNextInt()){ 
    out.printf("%d", c.nextInt()); 
    out.println(); 
c.close(); 
} 
out.close(); 
System.out.println("input written into file successfully!"); 
    } 
    catch(FileNotFoundException e){ 
System.out.println("The file not found"); 


    } 
} 

    } 

我运行该程序后，文件ABC的内容丢失，然后我进行扫描功能输入1 2 3 4 5，它示出了误差修改：

1 2 3 4 5 
    Exception in thread "main" java.lang.IllegalStateException: Scanner closed 
at java.util.Scanner.ensureOpen(Unknown Source) 
at java.util.Scanner.hasNext(Unknown Source) 
at java.util.Scanner.hasNextInt(Unknown Source) 
at java.util.Scanner.hasNextInt(Unknown Source) 
at Out.main(Out.java:17) 

它应该输出：

 1 
    2 
    3 
    4 
    5 

但似乎在PR没有找到该文件，我不确定哪个部分是错误的，请帮助，欢呼！

Answer 1

您正在致电hasNextInt()方法在关闭Scanner对象c，给你execption。

所以c.close();外应while环

Answer 2

您关闭循环本身中的Scanner对象！

试着把它放在循环之外。

while(c.hasNextInt()){ 
    out.printf("%d", c.nextInt()); 
    out.println(); 
} 
c.close(); 

你预期的输出结果是：

input written into file successfully! 

而不是：

1 
2 
3 
4 
5 

Answer 3

试试这个

while(c.hasNextInt()){ 
out.printf("%d", c.nextInt()); 
out.println(); 
} 
c.close();