java 基础 IO字符流

1.汉字存储占多少字节： 

public class IoTest {
    public static void main(String[] args) {
 
        String str = "abcd";
 
        String str1 = "吴危险学java";
 
        System.out.println("字符串转为byte数组：" + Arrays.toString(str.getBytes()));
        System.out.println(Arrays.toString(str1.getBytes(StandardCharsets.UTF_8)));
 
    }
}

2.编码和解码： 

 

 

public class IoTest {
    public static void main(String[] args) {
   
        String s="abcd";
        //我们要把abcd，装入字节数组中
        byte[] bytes = s.getBytes(StandardCharsets.UTF_8);        
        System.out.println(Arrays.toString(bytes));    
       //将byte字节数组，转成字符串类型    
        System.out.println(new String(bytes));
    }
}

 

3.字符流：

package login;
 
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
 
/*
将字符串转成字节
 */
public class IoTest {
    public static void main(String[] args) throws IOException {
 
 
        OutputStreamWriter outputStreamWriter = new
                OutputStreamWriter(new FileOutputStream("C:\\Users\\Administrator\\IdeaProjects\\mykt\\write.txt"));
        outputStreamWriter.write("已经开始有点晕了");
 
        System.out.println("写入数据成功");
        outputStreamWriter.close();
 
        System.out.println("--------------------------");
        System.out.println("开始读取数据");
 
        InputStreamReader inputStreamReader = new
                InputStreamReader(new FileInputStream("C:\\Users\\Administrator\\IdeaProjects\\mykt\\write.txt"), "utf-8");
        char[] charArr = new char[1024];
        int len;
        while ((len = inputStreamReader.read(charArr)) != -1) {
            System.out.println(new String(charArr, 0, len));
 
        }
        inputStreamReader.close();
    }
}

 

写入数据总结：

首先new 出fileoutputstream(路径)，可不必new出实例对象，直接作为下面的参数

再new outputstreamwriter()再将第一步new的fileoutputstream(路径)

new outputstreamwriter(new的fileoutputstream(路径))，new出实例对象后

.出write()方法，括号内即可写要写入的数据，最后一步，用实例对象，关闭资源

读取数据总结：

首先new 出fileinputstream(路径),可不必new出实例对象，直接作为下面的参数

再new inputstreamreader()再将第一步new的fileinputstream(路径) 

new inputstreamreader(new的fileinputstream(路径))  new出实例对象后

用实例对象.出read()方法，该方法若没有读取到数据返回值为-1，可用这个返回值，做循环条件，再创建整形变量，len，来计算数据长度

字节流<字符流

4.字符流5种写入方式： 

5.字符流读取数据： 

 6.数组转为字符串类型：Array.toString(某种类型的数组)

package login;
 
import java.util.Arrays;
 
public class Test2 {
    public static void main(String[] args) {
        char[] chars={'2','2','4','5'};
        int[] intArr={1,2,34,5,6,7};
        
        System.out.println(Arrays.toString(chars));
        System.out.println(Arrays.toString(intArr));
    }
}

7.FileReader类读取数据：

package login;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
public class Test15 {
    public static void main(String[] args) throws IOException {
        FileReader fileReader = new FileReader("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test14.txt");
        int len;
        char[] chars = new char[1024];
        while((len= fileReader.read(chars))!=-1){
            System.out.println(new String(chars,0,len));
        }
        fileReader.close();
    }
}

 

 

8.FileWriter类写入数据： 

package login;
 
import java.io.*;
 
public class Test15 {
    public static void main(String[] args) throws IOException {
        FileWriter fileWriter = new FileWriter("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt");
 
        fileWriter.write("可恶之前学的，不如后面的这好用");  
    }
}

9.字符缓冲流：

package login;
 
import java.io.*;
 
public class Test15 {
 
    public static void main(String[] args) throws IOException {
 
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
        //每次以8k缓冲容量大小写入数据到磁盘中
        bufferedWriter.write("hhhhhhhhh");
        bufferedWriter.close();
 
 
        BufferedReader bufferedReader =
                new BufferedReader(new FileReader("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
        char[] chars = new char[1024];
        int len;
        while((len=bufferedReader.read(chars))!=-1){
            System.out.println(new String(chars,0,len));
        }
        bufferedReader.close();
 
 
    }
}

 

10.字符缓冲流换行操作

 写入换行:newLine()

package login;
 
import java.io.*;
 
public class Test15 {
 
    public static void main(String[] args) throws IOException {
 
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
        //每次以8k缓冲容量大小写入数据到磁盘中
        for (int i = 0; i < 10; i++) {
            bufferedWriter.write("第"+i+"行");
            bufferedWriter.newLine();
        }
 
        bufferedWriter.close();
 
 
        BufferedReader bufferedReader =
                new BufferedReader(new FileReader("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
        char[] chars = new char[1024];
        int len;
        while((len=bufferedReader.read(chars))!=-1){
            System.out.println(new String(chars,0,len));
        }
        bufferedReader.close();
 
 
    }
}

 

 读取换行：readLine()

 

package login;
 
import java.io.*;
 
public class Test15 {
 
    public static void main(String[] args) throws IOException {
 
//        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
//        //每次以8k缓冲容量大小写入数据到磁盘中
//        for (int i = 0; i < 10; i++) {
//            bufferedWriter.write("第"+i+"行");
//            bufferedWriter.newLine();
//        }
//
//        bufferedWriter.close();
 
 
        BufferedReader bufferedReader =
                new BufferedReader(new FileReader("C:\\Users\\Administrator\\IdeaProjects\\mykt\\test15.txt"));
       String s;
        while((s=bufferedReader.readLine())!=null){
            System.out.println(s);
       }
        bufferedReader.close();
 
    }
}

 

 11.拷贝复制java文件：

package login;
 
import java.io.*;
 
public class Test15 {
    /*
    将E:\wwx\xx\目录下的Student.java复制到E:\wwx\recieve中
     */
    public static void main(String[] args) throws IOException {
 
        BufferedReader bufferedReader = new BufferedReader(new FileReader("E:\\wwx\\xx\\Student.java"));
 
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("E:\\wwx\\recieve\\Student.java"));
 
        String s;
        while ((s = bufferedReader.readLine()) != null) {
            bufferedWriter.write(s);
            bufferedWriter.newLine();//该方法会根据电脑系统自动换行
        }
        bufferedReader.close();
        bufferedWriter.close();
 
    }
}