Java学习笔记（十五）

た入场券 2023-09-30 10:21 107阅读 0赞

**目录**

一：字符缓冲流

二： IO流小结

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## 一：字符缓冲流 ##

**1.1 字符缓冲流的概述：**

>  *  BufferedWriter:将文本写入字符输出流，缓冲字符，以提供单个字符，数组和字符串的高效写入，可以指定缓冲区大小，或者可以接受默认大小。默认值足够大，可以用于大多数用途
>  *  BufferedReader:从字符输入流读取文本，缓冲字符，以提供字符，数组和行的高效读取，可以指定缓冲区大小，或者可以使用默认大小。默认值足够大，可用于大多数用途。

构造方法：

>  *  BufferedWriter(Writer out)
>  *  BufferedReader(Reader in)

--------------------

import java.io.*;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
           //BufferedWriter bw=new BufferedWriter(new FileWriter("mokuai-06\\bw.txt"));
           /*bw.write("hello");
           bw.write("\n");
           bw.write("world");
           bw.write("\n");
           bw.write("java");*/
    
           //bw.close();
    
            BufferedReader br=new BufferedReader(new FileReader("mokuai-06\\bw.txt"));
            //一次读取一个字符
            /*int len;
            while((len=br.read())!=-1){
                System.out.print((char)len);
            }*/
            //一次读取一个字符数组
            int len;
            char[] chs=new char[1024];
            while((len=br.read(chs))!=-1){
                System.out.print(new String(chs,0,len));
            }
            br.close();
        }
    }

--------------------

**1.2 案例：复制Java文件（字符缓冲流改进版）**

import java.io.*;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
            //根据数据源创建字符缓冲流输入流对象
            BufferedReader br=new BufferedReader(new FileReader("mokuai-06\\Farmers.java"));
            //根据目的地创建字符缓冲流输出流对象
            BufferedWriter bw=new BufferedWriter(new  FileWriter("mokuai-06\\copy.java"));
    
            //读写数据，复制文件
            //一次读写一个字符数据
            int ch;
            while((ch=br.read())!=-1){
                bw.write(ch);
            }
    
            //释放资源
            bw.close();
            br.close();
        }
    }

**1.3 字符缓冲流特有功能**

>  *  BufferedWriter:void newLine():写一行分隔符，行分隔符字符串由系统属性定义。
>  *  BufferedReader:public String readLine():读一行文字。结果包含行的内容的字符串，不包括任何行终止字符，如果流的结尾已经到达，则为null。

--------------------

import java.io.*;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
            //创建字符缓冲流对象
            Writer out;
            BufferedWriter bw=new BufferedWriter(new FileWriter("mokuai-06\\bw.txt"));
    
            
            for(int i=0;i<10;i++){
                bw.write("hello"+i);
                bw.newLine();
                bw.flush();
            }
    
            BufferedReader br=new BufferedReader(new FileReader("mokuai-06\\bw.txt"));
            String line;
            while((line=br.readLine())!=null){
                System.out.println(line);
            }
    
            //释放资源
            bw.close();
            br.close();
    
        }
    }

--------------------

**1.4 案例：复制Java文件（字符缓冲流特有功能改进版）**

import java.io.*;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
            //创建字符缓冲流对象
            Writer out;
            BufferedWriter bw=new BufferedWriter(new FileWriter("mokuai-06\\Copy.java"));
            BufferedReader br=new BufferedReader(new FileReader("mokuai-06\\Farmers.java"));
            String line;
            while((line=br.readLine())!=null){
                bw.write(line);
                bw.newLine();
            }
    
    
    
    
            //释放资源
            bw.close();
            br.close();
    
        }
    }

--------------------

## **二： IO流小结** ##

**2.1 字节流小结：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_15_color_FFFFFF_t_70_g_se_x_16][]**

**2.2 字符流小结：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_17_color_FFFFFF_t_70_g_se_x_16][]**

--------------------

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_15_color_FFFFFF_t_70_g_se_x_16 1][]

--------------------

import java.io.*;
    import java.util.ArrayList;
    import java.util.Random;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
    
            Random r=new Random();
    
            BufferedReader br=new BufferedReader(new FileReader("mokuai-06\\bw.txt"));
            ArrayList<String> array=new ArrayList<>();
            String line;
            while((line=br.readLine())!=null){
                array.add(line);
            }
    
            int n=r.nextInt(0,array.size());
            System.out.println(array.get(n));
        }
    }

**2.3 案例：集合到文件（改进版）**

--------------------

import java.io.*;
    import java.util.ArrayList;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
            //创建ArrayList集合
            ArrayList<student> array=new ArrayList<>();
            //创建学生对象
            student s1=new student("itheima001","小花",18,"南城");
            student s2=new student("itheima002","小白",19,"北城");
            student s3=new student("itheima003","小黑",20,"东城");
    
            array.add(s1);
            array.add(s2);
            array.add(s3);
    
            BufferedWriter bw=new BufferedWriter(new FileWriter("mokuai-06\\bw.txt"));
            for(student s:array){
                StringBuilder sb=new StringBuilder();
                sb.append(s.getId()).append(",").append(s.getName()).append(",").append(s.getAge()).append(",").append(s.getAddress());
                bw.write(sb.toString());
                bw.newLine();
                bw.flush();
            }
            bw.close();
        }
    }
    class student{
        private String id;
        private String name;
        private int age;
        private String address;
    
        public student(String id, String name, int age, String address) {
            this.id = id;
            this.name = name;
            this.age = age;
            this.address = address;
        }
    
        public String getId() {
            return id;
        }
    
        public void setId(String id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    }

--------------------

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_16_color_FFFFFF_t_70_g_se_x_16][]

--------------------

import java.io.*;
    import java.util.ArrayList;
    import java.util.Comparator;
    import java.util.Iterator;
    import java.util.TreeSet;
    
    class Main1 {
        public static void main(String[] args) throws IOException {
            TreeSet<student> ts=new TreeSet<>(new Comparator<student>() {
                @Override
                public int compare(student s1, student s2) {
                    int num=s1.sum()-s2.sum();
                    int num1=num==0?s1.getName().compareTo(s2.getName()):num;
                    return num1;
                }
            });
            //添加学生对象
            student s1=new student("小花",87,88,99);
            student s2=new student("小白",87,88,99);
            student s3=new student("小黑",67,88,99);
            ts.add(s1);
            ts.add(s2);
            ts.add(s3);
    
            BufferedWriter bw=new BufferedWriter(new FileWriter("mokuai-06\\bw.txt"));
            Iterator<student> it=ts.iterator();
            while(it.hasNext()){
                student s=it.next();
                StringBuilder sb=new StringBuilder();
                sb.append(s.getName()).append(",").append(s.getCh()).append(",").append(s.getMa()).append(",").append(s.getEn());
                bw.write(sb.toString());
                bw.newLine();
                bw.flush();
            }
            bw.close();
            }
    
        }
    
    class student{
       private String name;
       private int ch;
       private int ma;
       private int en;
    
        public student(String name, int ch, int ma, int en) {
            this.name = name;
            this.ch = ch;
            this.ma = ma;
            this.en = en;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getCh() {
            return ch;
        }
    
        public void setCh(int ch) {
            this.ch = ch;
        }
    
        public int getMa() {
            return ma;
        }
    
        public void setMa(int ma) {
            this.ma = ma;
        }
    
        public int getEn() {
            return en;
        }
    
        public void setEn(int en) {
            this.en = en;
        }
        public int sum(){
            return this.ch+this.ma+this.en;
        }
    }

**2.4 案例：复制单级文件**

--------------------

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_13_color_FFFFFF_t_70_g_se_x_16][]

--------------------

import java.io.*;
    
    class Main1{
        public static void copyFile(File srcFile,File destFile) throws IOException {
    
            BufferedInputStream bis=new BufferedInputStream(new FileInputStream(srcFile));
            BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(destFile));
            int len;
            byte[] bys=new byte[1024];
            while((len=bis.read(bys))!=-1){
                bos.write(bys,0,len);
                bos.flush();
            }
            bis.close();
            bos.close();
        }
        public static void main(String[] args) throws IOException {
            //创建数据源目录File对象
            File srcFolder=new File("D:\\IT");
    
            //获取数据源目录File对象的名称
            String srcFolderName=srcFolder.getName();
    
            //创建目的地目录File对象，路径名是模块名+IT组成
            File destFolder=new File("mokuai-06",srcFolderName);
    
            //判断目的地目录对应的File是否存在，如果不存在，就创建一个
            if(!destFolder.exists()){
                destFolder.mkdir();
            }
    
            //获取数据源目录下所有文件的File数组
            File[] listFiles=srcFolder.listFiles();
    
            //遍历File数组，得到每一个File对象，该File对象，其实就是数据源文件
            for(File srcFile:listFiles){
                //数据源文件：------
    
                //获取数据源文件File对象的名称
                String srcFileName= srcFile.getName();
    
                //创建目的地文件File对象，路径名是目的地目录+文件名
                File destFile=new File(destFolder,srcFileName);
    
                //复制文件
                copyFile(srcFile,destFile);
    
            }
        }
    
    }

--------------------

（PS：文章照片均截至黑马程序员java全套视频）

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