java 期末考试笔记

文章目录

• 输入输出流
• • 字符流
  • 字符流 + 缓冲流
  • 字节输入输出流 + utf-8
• 面向对象
• • 长方形求面积
  • • Test类
    • 长方形类
• 多线程
• • 继承thread
  • • Test
    • run
  • Runnable接口
  • • Tesr
    • run

输入输出流

字符流

package qimo;

import java.io.*;

public class Inout {
    public static void main(String[] args){
        File i = new File("D:/java0/tzg","123.txt");
        File j = new File("D:/java0/tzg","456.txt");
        try
        {
            FileReader in = new FileReader(i);
            FileWriter out = new FileWriter(j);
            
            char[] st = new char[10];
            int len=0;

            while((len = in.read(st))>0)
            {
                String str = new String(st, 0, len);
                out.write(st);
                System.out.print(str);  // 输出每次 读入文件的内容
            }
            out.close();     // 先关  out  再关 in
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println(e.toString());
        }
    }
}

字符流 + 缓冲流

package qimo;

import java.io.*;

public class Inout {
    public static void main(String[] args){
        File i = new File("D:/java0/tzg","123.txt");
        File j = new File("D:/java0/tzg","456.txt");
        try
        {
            FileReader in = new FileReader(i);
            FileWriter out = new FileWriter(j);

            BufferedReader in1 = new BufferedReader(in);      //    缓冲流
            BufferedWriter out1 = new BufferedWriter(out);

            String st = null;

            while((st = in1.readLine()) != null)        //    一次读一行
            {
                String str = new String(st);
                out1.write(st);
                out1.newLine();
                System.out.print(str+'\n');  // 输出每次 读入文件的内容
            }

            //   先关out1  再关out
            out1.close();    //   先关out 再关 in
            out.close();    
            
            in1.close();
            in.close();

        } catch (IOException e) {
            e.printStackTrace();
            System.out.println(e.toString());
        }
    }
}

字节输入输出流 + utf-8

package qimo;

import java.io.*;

public class inoutzijie {
     public static void  main(String[] args){
          File i = new File("D:/java0/tzg/","123.txt");
          File j = new File("D:/java0/tzg/","456.txt");
          try {
               FileInputStream in1 = new FileInputStream(i);
               FileOutputStream out1 = new FileOutputStream(j,true);
               //   FileOutputStream(String name, boolen append)  append 为true  
               //在原文件后面追加  默认false 刷新文件 再写入 
               InputStreamReader in2 = new InputStreamReader(in1,"utf-8");
               OutputStreamWriter out2 = new OutputStreamWriter(out1,"utf-8");

               BufferedReader in3 = new BufferedReader(in2);
               BufferedWriter out3 = new BufferedWriter(out2);

               String st=null;
               while((st = in3.readLine()) != null)
               {
                     String str = new String(st);
                     out3.write(st);
                     out3.newLine();
                     System.out.println(str);
               }

               out3.close();
               out2.close();
               out1.close();
               in3.close();
               in2.close();
               in1.close();
          } catch (FileNotFoundException e) {
               e.printStackTrace();
          } catch (UnsupportedEncodingException e) {
               e.printStackTrace();
          } catch (Exception e) {
               e.printStackTrace();
          }

     }


}

面向对象

长方形求面积

Test类

package qimo;

import java.util.Scanner;

public class Tes {
    public static void main(String[] agrs){
        Scanner re = new Scanner(System.in);
        System.out.print("请输入长：");
        double a = re.nextDouble();
        System.out.print("请输宽：");
        double b = re.nextDouble();
        Rectangle r = new Rectangle(a,b);
        System.out.println("长方形的面积是："+r.area());
    }
}

长方形类

package qimo;

public class Rectangle {
    double a;
    double b;
    Rectangle(){}
    Rectangle(double a,double b)
    {
        this.a = a;
        this.b = b;
    }
    public  void setA(double a)
    {
        this.a = a;
    }
    public void setB(double b)
    {
        this.b = b;
    }
    public double getA()
    {
        return a;
    }
    public  double getB()
    {
        return b;
    }
    public double area()
    {
        return a * b;
    }

}

多线程

继承thread

Test

package qimo;

public class Test2 {
    public static void main(String[] args){
      Carthead car = new Carthead();
      car.start();
    }
}

run

package qimo;

public class Carthead extends Thread {
    int number=20;
    public void run(){
        for(int i=1;i<=number;i++)
        {
            System.out.println("卖出了"+i+"火车票");
             if(i == 0){}
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

Runnable接口

Tesr

package qimo;

public class Test3 {
    public static void main(String[] args){
        Carthead2 ca = new Carthead2();
        Thread car = new Thread(ca);
        car.start();
    }
}

run

package qimo;

public class Carthead2 implements Runnable{

    @Override
    public void run() {
        int n=20;
        for(int i=1;i<=n;i++)
        {
            System.out.println("火车票剩余"+(n-i));
            if( i == 20 ){System.out.println("已售完");}
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}