小编Ara*_*ras的帖子

我是java的新手.我大概3天前开始了.我想制作一行随机字符并将它们放入一个字符串中.谢谢.

    import java.util.Random;
      public class test{
      public static void main (String[]args){

final String alphabet = "abcdefghigklmnopqrstuvwxyz";
final int N = alphabet.length();
Random r = new Random();

for (int i = 0; i < 50; i++) {
    String s = alphabet.charAt(r.nextInt(N));
    // System.out.println(alphabet.charAt(r.nextInt(N)));
}}}

我有一个简单的应用程序,但它会废弃一个文本文件(这只是练习)我还只有3天的Java.问题是在运行程序之前没有错误然后它会抛出异常并停止.谢谢.这是例外:

      java.io.IOException: Stream closed
    at sun.nio.cs.StreamEncoder.ensureOpen(Unknown Source)
    at sun.nio.cs.StreamEncoder.write(Unknown Source)
    at sun.nio.cs.StreamEncoder.write(Unknown Source)
    at java.io.OutputStreamWriter.write(Unknown Source)
    at java.io.Writer.write(Unknown Source)
    at test.main(test.java:18)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at 
     edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)

这是代码.

import java.io.FileWriter;
import java.util.Random;
import java.io.IOException;
public class test {
    public static void main(String[] args) throws IOException {

        final String alphabet = "abcdefghigklmnopqrstuvwxyz";
        final int N = alphabet.length();
        Random r = new Random();

        FileWriter file = new FileWriter("hello.txt");
        String sb = " ";
        for …

我想做一些像计算器擦除按钮之类的事情，或者更具体地说，我想在更改文本框而不是写入数字时删除最后一个字符。就像在 Java 中一样，我猜您可以使用 CharAt() 方法，但是 C# 怎么样？