Java I/O操作学习笔记

书上写的有点乱，所以就自己总结了一下，主要参考：http://www.cnblogs.com/qianbi/p/3378466.html

1.从文件读出和写入：

 import java.io.*;
 import java.util.*;
 public class FileDemo{
     private Formatter f2;
     public void Fileexists(){
         File f1 = new File("D:\\test2.txt");

         //查看文件test2.txt是否存在
         if(f1.exists())
             System.out.println(f1.getName() + " exists");
         else
             System.out.println("this thing does not exists");

     }

     public void WriteFile(){
         BufferedWriter out = null;
         try{
             out = new BufferedWriter(new FileWriter("fred.txt"));
             out.write("20 sunshineatnoon");
             out.newLine();
             out.write("21 moment");
         }catch(Exception e){
             e.printStackTrace();
         }finally{
             try{
                 out.close();
             }catch(Exception e){

             }
         }
     }

     public void closeFile(){
         f2.close();
     }

     //按行读取文件
     public void ReadFile(){
         FileReader reader = null;
         BufferedReader br = null;
         try{
             reader = new FileReader("fred.txt");
             br = new BufferedReader(reader);
             String s1 = null;

             while((s1 = br.readLine()) != null){
                 System.out.printf("%s\n",s1);
             }

         }catch(Exception e){
             e.printStackTrace();
         }finally{
             try{
                 reader.close();
             }catch(Exception e){

             }
         }
     }
 }

2.从控制台输入

public void ReadFromConsle(){
    Scanner sc = new Scanner(System.in);
    System.out.println("输入数字:");
    System.out.println("输入的数字为："+sc.nextInt());

    System.out.println("输入字符串：");
    System.out.println("输入的字符串为："+sc.next());
}

类似的还有sc.nextDouble()等，如果不知道什么输入，直接按照字符串处理。