字符流=字节流+编码表
Java为什么可以区分字母和汉字
package day3;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Array;
import java.util.Arrays;
public class Test {
public static void main(String[] args) throws UnsupportedEncodingException {
String s1="abc";
String s2="你好";
byte[] byt1 = s1.getBytes();
byte[] byt2 = s2.getBytes();
byte[] byt3 = s2.getBytes("GBK");
System.out.println(Arrays.toString(byt1));
System.out.println(Arrays.toString(byt2));
System.out.println(Arrays.toString(byt3));
}
}
我们发现中文都是负数 而英文都是正数
UFT-8中 三个字节对应一个中文字
GBK里面两个字节对应一个中文字
字符流的乱码现象
package day3;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Array;
import java.util.Arrays;
public class Test {
public static void main(String[] args) throws UnsupportedEncodingException {
String s1 = new String("你好");
byte[] bytes = s1.getBytes("UTF-8");
String s2 = new String(bytes,"GBK");
System.out.println(s2);
}
}
为什么会产生乱码现象呢？
因为将字符串转换成字节数组的时候用的是UTF-8一个汉字三个字节
而将字节数组转换为字符的时候我们用的是GBK两个字节 一个汉字
当两者都是一样的时候不会乱码
package day3;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Array;
import java.util.Arrays;
public class Test {
public static void main(String[] args) throws UnsupportedEncodingException {
String s1 = new String("你好");
byte[] bytes1 = s1.getBytes("UTF-8");
String s2 = new String(bytes1,"UTF-8");
System.out.println(s2);
byte[] bytes2 = s1.getBytes("GBK");
String s3 = new String(bytes2,"GBK");
System.out.println(s3);
}
}
*Java中默认采用UTF-8
字符流写数据的五种方式
-
void write(int c)写一个字符
-
void write(char[] cbuf)写入一个字符数组
-
void write(char[] cbuf,int off,int len)写入一个字符数组的一部分
-
voif write(String str)写入一个字符串
-
void (String str,int off,int len)写入一个字符串的一部分
package day3;
import java.io.*;
public class Test {
public static void main(String[] args) throws IOException {
FileOutputStream fos = new FileOutputStream("write.txt");
OutputStreamWriter osw = new OutputStreamWriter(fos);
osw.write(97);
osw.write(98);
osw.write(99);
osw.flush();
char[] c = {'\n','c','b','s'};
osw.write(c);
osw.flush();
osw.write("\nhello\n");
osw.write("wworldd",1,5);
osw.close();
}
}
注意： 字符流写完要输出刷新 不然文本上不会有显示 close()是先刷新再关闭 所有close()有刷新的功能
字符流读数据
-
int read（）一次读一个数据
-
int read（char[] cbuf）一次读一个字符串数组
package day3;
import java.io.*;
public class Test {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("write.txt");
InputStreamReader isr = new InputStreamReader(fis);
int r;
while ((r=isr.read())!=-1){
System.out.print((char)r);
}
char[] c = new char[1024];
isr.close();
}
}
package day3;
import java.io.*;
public class Test {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("write.txt");
InputStreamReader isr = new InputStreamReader(fis);
char[] c = new char[1024];
int len;
while ((len=isr.read(c))!=-1){
System.out.println(new String(c,0,len));
}
isr.close();
}
}
两种读的方式
字符缓冲流
BufferedWriter 将文本写入字符输出流中
BufferedReader 从字符输入流读取文本
package day3;
import java.io.*;
public class Test {
public static void main(String[] args) throws IOException {
FileWriter fw = new FileWriter("write.txt");
BufferedWriter bw = new BufferedWriter(fw);
bw.write("hello\n");
bw.flush();
FileReader fr = new FileReader("write.txt");
BufferedReader br = new BufferedReader(fr);
char[] ch = new char[1024];
int len;
while ((len=br.read(ch))!=-1){
System.out.println(new String(ch,0,len));
}
br.close();
bw.close();
}
}
