我试图让我的程序创建另一个文件,可以由用户命名,并打印出用户想要打印的随机数字。不幸的是,当我运行我的程序时,它一直工作到最后 "你想使用什么文件名",其中程序指出
"File not found java.io.FileNotFoundException: (句柄无效)"
我想知道怎样才能让程序实际创建文件,并让用户为文件选择自己的名字。
import java.io.*;
import java.util.*;
public class chooseRandNum{
public static void main(String[] args){
Random rand = new Random();
Scanner key = new Scanner(System.in);
System.out.println("How many random numbers do you want? ");
int totalRand = key.nextInt();
System.out.println("What is the smallest random number? ");
int smallRand = key.nextInt();
System.out.println("What is the largest random number? ");
int largeRand = key.nextInt();
System.out.println("What filename do you want to use? ");
String fname = key.nextLine();
File outputFile = new File(fname);
PrintStream outputStream = null;
try{
outputStream = new PrintStream(outputFile);
}
catch (Exception e){
System.out.println("File not found " + e);
System.exit(1);
}
int n = rand.nextInt(largeRand - smallRand + 1);
for(int i = 0; i <= 5; i++){
for(int j = 0; j <= totalRand; j++){
outputStream.print(n + ",");
}
outputStream.println();
}
}
}
String fname = key.nextLine();
应该是 String fname = key.next();
代码还有其他问题,但这解决了问题中的问题。
从JavaDoc:
nextLine()
/**
* Advances this scanner past the current line and returns the input
* that was skipped.
*
* This method returns the rest of the current line, excluding any line
* separator at the end. The position is set to the beginning of the next
* line.
*
* <p>Since this method continues to search through the input looking
* for a line separator, it may buffer all of the input searching for
* the line to skip if no line separators are present.
*
* @return the line that was skipped
* @throws NoSuchElementException if no line was found
* @throws IllegalStateException if this scanner is closed
*/
next()
/**
* Finds and returns the next complete token from this scanner.
* A complete token is preceded and followed by input that matches
* the delimiter pattern. This method may block while waiting for input
* to scan, even if a previous invocation of {@link #hasNext} returned
* {@code true}.
*
* @return the next token
* @throws NoSuchElementException if no more tokens are available
* @throws IllegalStateException if this scanner is closed
* @see java.util.Iterator
*/
在这些语句之后
System.out.println("What is the largest random number? ");
int largeRand = key.nextInt();
把这个
key.nextLine(); // clear lingering new line
然后继续。
System.out.println("What filename do you want to use? ");
String fname = key.nextLine();
并在这个网站上查看以下内容: 扫描仪的使用