[文件操作 生成20个文件：每个包含100字节的随机数]

-(void)create{
    for (int i=0; i<20;i++) {
        NSString *fp = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/%i.txt",i]];
        NSString *ss= @"";
        
        for(int i=0;i<100;i++){
            int value = arc4random() % 10;
            NSString *svalue=[NSString stringWithFormat:@"%i",value];
            ss=[ss stringByAppendingString:svalue];
        }
        [ss writeToFile:fp atomically:YES encoding:NSUTF8StringEncoding error:nil];
    }
    NSLog(@"生成成功");
}

#include <iostream>
#include <cstdlib>
#include <fstream>
#include <ctime>
#include <string>
#include <sstream>
using namespace std;

int main(int argc, const char * argv[]) {
    //产生20个100B文件
    srand((unsigned)time(NULL));
    for (int j=0; j<20;j++ ) {
        //定义文件路径，生成不同文件名的文件
        //C++String的动态性能真是差。。
        string a="/Users/way/Desktop/test/yes[",b,c="].txt";
        stringstream ss;
        ss<<j;
        ss>>b;
        string name=a+b+c;
        ofstream of(name);
        
        //随机产生100个数字写入文件
        for (int i=0; i<100; i++) {
            of<<rand()%10;
        }
        of.close();
    }
    cout<<"生成成功"<<endl;
    return 0;
}

import java.io.*;
public class Main {
    public static void main(String[] args){
        try{
            for (int j=0; j<20;j++ ) {
                //定义文件输出流
                String a="/Users/way/Desktop/test2/yes[",b,c="].txt";
                b=Integer.toString(j);
                String nameString=a+b+c;                
                FileWriter wf=new FileWriter(nameString);
                
                //定义字符输出流
                BufferedWriter bw=new BufferedWriter(wf);
                String ss ="";
                for (int i=0;i<100;i++){
                    int num=(int) (Math.random()*10);
                    ss=ss+Integer.toString(num);
                }
                bw.write(ss);
                bw.close();
                wf.close();
                System.out.println(ss);
            }
            System.out.println("生成成功");
        }catch(IOException ie){
            System.out.println(ie);
        }catch(Exception e){
            System.out.println(e);
        }    
    }
}