Java IO流(转换流的字符编码)

编码:字符串变成字节数组，解码:字节数组变成字符串。String-->byte[];str.getBytes[charsetName];byte[] --> String:new String(byte[],charsetName);

import java.io.*;

public class EncodeStream {
    public static void main(String[] args) throws IOException
    {
//        writeText();
        readText();
    }
    public static void readText() throws IOException
    {
        InputStreamReader isr = new InputStreamReader(new FileInputStream("utf.txt"),"UTF-8");
        char[] buf = new char[10];
        int len = isr.read(buf);
        String str = new String(buf,0,len);
        System.out.println(str);
        isr.close();
    }
    public static void writeText() throws IOException
    {
        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("utf.txt"),"UTF-8");
        osw.write("你好");
        osw.close();
    }
}
//输出
你好

import java.io.*;

public class EncodeStream {
    public static void main(String[] args) throws IOException
    {
//        writeText();
        readText();
    }
    public static void readText() throws IOException
    {
        InputStreamReader isr = new InputStreamReader(new FileInputStream("utf.txt"),"GBK");
        char[] buf = new char[10];
        int len = isr.read(buf);
        String str = new String(buf,0,len);
        System.out.println(str);
        isr.close();
    }
    public static void writeText() throws IOException
    {
        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("utf.txt"),"UTF-8");
        osw.write("你好");
        osw.close();
    }
}
//输出
浣犲ソ

编码解码格式错乱，没有对应。

import java.io.IOException;
import java.util.Arrays;

public class EncodeDemo0 {
    public static void main(String[] args) throws IOException
    {
        String s = "哈哈";
        byte[] b1 = s.getBytes("GBK");
        System.out.println(Arrays.toString(b1));
        String s1 = new String(b1,"utf-8");
        System.out.println("s1="+s1);
        byte[] b2 = s1.getBytes("utf-8");
        System.out.println(Arrays.toString(b2));
        String s2 = new String(b2,"gbk");
        System.out.println("s2="+s2);
    }
}
//输出
[-71, -2, -71, -2]
s1=����
[-17, -65, -67, -17, -65, -67, -17, -65, -67, -17, -65, -67]
s2=锟斤拷锟斤拷

public class EncodeDemo1 {
    public static void main(String[] args) throws Exception
    {
        String s = "联通";
        byte[] by = s.getBytes("gbk");
        for (byte b :by)
        {
            System.out.println(Integer.toBinaryString(b&255));
        }
    }
}
//输出
11000001
10101010
11001101
10101000

110，10，0和1110，10，10符合utf-8编码格式。

有五个学生，每个学生有3门课的成绩，从键盘输入以上数据(包括姓名，三门课成绩)，输入的格式:如：zhangsan,30,40,60计算出总成绩。并把学生的信息和计算出的总分数高低顺序存放在磁盘文件sud.txt中。

• 1.描述学生对象。
• 2.定义一个可操作学生对象的工具类。
  思想:
• 1.通过获取键盘录入一行数据，并将该行中的信息取出封装成学生对象。
• 2.因为学生有很多，那么就需要存储，使用到集合。因为要对学生的总分排序。所以可以使用TreeSet。
• 3.将集合的信息写入到一个文件中。

import java.io.*;
import java.util.Collections;
import java.util.Comparator;
import java.util.Set;
import java.util.TreeSet;

class Student12 implements Comparable<Student12>
{
    private String name;
    private int ma,cn,en;
    private int sum;
    Student12(String name,int ma,int cn,int en)
    {
        this.name = name;
        this.ma = ma;
        this.cn = cn;
        this.en = en;
        sum = ma + cn + en;
    }
    public int compareTo(Student12 s)
    {
        int num = new Integer(this.sum).compareTo(new Integer(s.sum));
        if (num == 0)
            return this.name.compareTo(s.name);
        return num;

    }
    public String getName()
    {
        return name;
    }
    public int getSum()
    {
        return sum;
    }
    public int hashCode()
    {
        return name.hashCode()+sum*78;
    }
    public boolean equals(Object obj)
    {
        if (!(obj instanceof Student))
            throw new ClassCastException("类型不匹配");
        Student12 s = (Student12) obj;
        return this.name.equals(s.name) && this.sum == s.sum;
    }
    public String toString()
    {
        return "student["+name+", "+ma+", "+cn+", "+en+"]";
    }
}
class StudentInfoTool
{
    public static Set<Student12> getStudents() throws IOException
    {
        return getStudents(null);
    }
    public static Set<Student12> getStudents(Comparator cmp)throws IOException
    {
        BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in));
        String line = null;
        Set<Student12> stus = null;
        if (cmp == null)
            stus = new TreeSet<Student12>();
        else
            stus = new TreeSet<Student12>(cmp);
        while ((line = bufr.readLine())!=null)
        {
            if ("over".equals(line))
                break;
            String[] info = line.split(",");
            Student12 stu = new Student12(info[0],Integer.parseInt(info[1]),Integer.parseInt(info[2]),Integer.parseInt(info[3]));
            stus.add(stu);
        }
        bufr.close();
        return stus;
    }
    public static void write2File(Set<Student12> stus)throws IOException
    {
        BufferedWriter bufw = new BufferedWriter(new FileWriter("stusinfo.txt"));
        for (Student12 stu : stus)
        {
            bufw.write(stu.toString()+"\t");
            bufw.write(stu.getSum()+"");
            bufw.newLine();
            bufw.flush();
        }
        bufw.close();
    }
}
public class StudentInfoTest {
    public static void main(String[] args)throws IOException
    {
        Comparator<Student12> cmp = Collections.reverseOrder();
        Set<Student12> stus = StudentInfoTool.getStudents(cmp);
        StudentInfoTool.write2File(stus);
    }
}
//输入
zhangsan,12,34,78
lisi,14,34,78
wangwu,34,56,78
zhaoliu,54,64,87
zhouqi,87,87,89
over

Snip20191003_5.png