java_IO_2

1.字节流  InputStream（抽象类）  

package ioStudy;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

/*
1.创建源
2.选择流
3.操作
4.释放资源
*/
public class IOstudy2 {
    public static void main(String[] args) {
        File file = new File("test.txt");    //创建源

        InputStream is = null;

        try {
            is = new FileInputStream(file);     //  选择流
            int temp;
            while ((temp = is.read()) != -1) {      //一次读一个字节  如果包含中文可能会出现乱码  考虑使用字符流
                System.out.print((char) temp);    //操作
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(is!=null) {
                try {
                    is.close();        //释放资源
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}

package ioStudy;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

/*
1.创建源
2.选择流
3.操作
4.释放资源
*/
public class IOstudy3 {
    public static void main(String[] args) {
        File file = new File("test.txt");
        InputStream is = null;
        try {
            is = new FileInputStream(file);
            byte[] buffer = new byte[5];
            int len;
            while ((len = is.read(buffer)) != -1) {    //一次读取多个
                String s = new String(buffer,0,len);
                System.out.print(s);
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(is!=null) {
                try {
                    is.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}

---

2.OutputStream

 

package ioStudy;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/*
1.创建源
2.选择流
3.操作
4.释放资源
*/
public class IOstudy4 {
    public static void main(String[] args) {
        File file = new File("output.txt"); // 不存在会自动创建
        OutputStream os = null;

        try {
            os = new FileOutputStream(file,true);  //开启向后追加  不然每次都删掉原来的 再写  默认的是false
            String temp = "hello world!
";
            byte[] b = temp.getBytes();
            os.write(b, 0, b.length);
            os.flush();   //刷新内存
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}

3.实现文件的copy

package ioStudy;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/*
1.创建源
2.选择流
3.操作
4.释放资源
*/
public class Copy {
    public static void main(String[] args) {
        copy("test.txt","testcopy.txt");
    }

    public static void copy(String source, String destination) {
        File src = new File(source);
        File dest = new File(destination);
        InputStream is = null;
        OutputStream os = null;
        try {
            is = new FileInputStream(src);
            os = new FileOutputStream(dest);

            byte[] buffer = new byte[1034];
            int len;
            while ((len = is.read(buffer)) != -1) {
                os.write(buffer, 0, len);
                os.flush();
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            // 流关闭的原则 先打开的后关闭
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}