1、编码表
以什么表写，就以什么表读
例 public static void readText()throws IOException
{
InputStreamReader isr=new InputStreamReader(new FileInputStream("E:\\java_heima\\gbk.txt"),"gbk");
char[] buf=new char[20];
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("E:\\java_heima\\gbk.txt"),"GBK");
osw.write("Hello,早上好");
osw.close();
}
2、
编码 ：字符串变成字节数组
string-->byte[]; str.getBytes();
解码 ：字节数组变成字符串
byte[]-->String; new String(byte[])
3、练习
package com.deu.Twenty_One;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Set;
import java.util.TreeSet;
/*
* 有5个学生，每个学生有3门成绩，
* 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,10,10,10计算出总成绩
* 并把学生的信息和计算出的总分按高低顺序存放在磁盘文件“stud.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
*
*/
class Student implements Comparable<Student>
{
private String name;
private int ma,cn,en;
private int sum;
Student(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 String getName() {
return name;
}
public int getSum(){
return sum;
}
//接口，要重写compareTo
public int compareTo(Student 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 toString()
{
return "student[ "+name+" ,"+ma+" ,"+cn+" ,"+en+" ]";
}
//
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");
Student s=(Student)obj;
return this.name.equals(s.name)&&this.sum==s.sum;
}
}
class StudentInfTool
{
public static Set<Student> getStudent() throws IOException
{
return getStudent(null);
}
public static Set<Student> getStudent(Comparator<Student> cmp) throws IOException
{
BufferedReader bufr=
new BufferedReader(new InputStreamReader(System.in));
String line=null;
Set<Student> stus=null;
if(cmp==null)
stus=new TreeSet<Student>();
else {
stus=new TreeSet<Student>(cmp);
}
while((line=bufr.readLine())!=null)
{
if("over".equals(line))
break;
String[] info=line.split(",");
Student stu=new Student(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<Student> stus)throws IOException
{
BufferedWriter bufw=new BufferedWriter(new FileWriter("E:\\java_heima\\stuinfo.txt"));
for(Student 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
{
// TODO Auto-generated method stub
Comparator<Student> cmp=Collections.reverseOrder();
Set<Student> stus=StudentInfTool.getStudent(cmp);
StudentInfTool.write2File(stus);
}
}
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