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HomeJavajavaTutorialjava IO stream - the use of output stream OutputString()

FileOutPutStream:子类,写出数据的通道

  步骤:

    1.获取目标文件

    2.创建通道(如果原来没有目标文件,则会自动创建一个)

    3.写入数据 write()

    4.释放资源

  注意:

    (1)如果目标文件不存在,那么会自己创建一个目标文件

    (2)如果目标文件存在,先将里面的数据清空,再写入数据

    (3)想在原有的数据上写入数据,则在创建通道的时候使用 构造方法:

       OutPutStream(File file,Boolean append),boolean值为true则可以

    (4)用 write(int a)方法写入数据,虽然接收的是int,但实际上只有一个字节的数据

      (操作的是低八位的,其他的全部丢掉)

//会自动导入一些包
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
//方式一
public static void writeData() throws IOException{
//1.找目标文件
File file = new File("C:\\Users\\bigerf\\Desktop\\文件夹\\writeTest.java");
//2.创建一个通道
FileOutputStream outputStream = new FileOutputStream(file);
//3.开始写入数据,
int a = 10; // int 型 4个字节 
outputStream.write(a); //注意这里每次只能输出一个字节
outputStream.write('b'); // char 类型
outputStream.write(5); 
// 0000-0000 0000-0000 0000-0001 1111-1111 == 511
int b = 511 ; //大于八位(9位)
outputStream.write(b); //实际结果 255,但没有显示
int c = 63; //小于八位(6位)
outputStream.write(c); //乱码
//4.关闭资源
outputStream.close();
}
//方式二
public static void writeData2() throws IOException{
//1.找目标文件
File file = new File("C:\\Users\\bigerf\\Desktop\\文件夹\\writeTest2.java");
//2.创建一个通道,(如果不存在路径中的文件,则会在这一步创建的文件)
//new FileOutputStream(file,true); /true表示在原来文本的基础上写入文本(反之则会先清空再写入)
FileOutputStream outputStream = new FileOutputStream(file,true); 
//3.创键一个字节数组
String str = "hello word";
//将字符串变为字节数组
byte[] b = str.getBytes();
//4.写入数据
outputStream.write(b); //hello word
//5.关闭资源
outputStream.close();
}

陌陌说:

  输入流与输出流可以实现对文件的拷贝,不妨试着实现

  (先将路径文件的数据拷贝写入到字节数组,再从字节数组写出道路径文件)

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