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();
}
}