字节输入输出流的应用

布满荆棘的人生 2023-08-17 16:09 82阅读 0赞

1、文件复制

用FileInputStream和FileOutPutStream实现文件的复制，此方法不能复制文件夹。

package pers.zhh.copy;
    
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    public class CopyDemo {
        public static void main(String[] args) throws IOException {
            FileInputStream fi = new FileInputStream("M:\\数据库.zip");
            FileOutputStream fo = new FileOutputStream("M:\\数据库1.zip");
            int num = 0;
            long startTime = System.currentTimeMillis();
            while ((num = fi.read()) != -1) {
                fo.write(num);
    
            }
            fo.close();
            fi.close();
            long endTime = System.currentTimeMillis();
            System.out.println("执行此程序用了" + (endTime - startTime) + "毫秒。");
        }
    }

![1392562-20190816202354544-732619518.png][]

（2）缓冲数组：

package pers.zzz.copy;
    
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    public class CopyDemo1 {
        public static void main(String[] args) throws IOException {
            FileInputStream fi = new FileInputStream("M:\\网页设计.zip");
            FileOutputStream fo = new FileOutputStream("M:\\网页设计3.zip");
            byte[] buf = new byte[1024];
            int len = 0;
            long startTime = System.currentTimeMillis();
            while ((len = fi.read(buf)) != -1) {
                fo.write(buf, 0, len); // 将数组中的指定长度的数据写入到输出流中。
            }
            fo.close();
            fi.close();
            long endTime = System.currentTimeMillis();
            System.out.println("执行此程序用了" + (endTime - startTime) + "毫秒。");
        }
    
    }

![1392562-20190816203329623-735988080.png][]

在第一个方法中，一次只能读取一个数据字节，复制只有几M的数据花了7s时间，效率极低。而第二种采用缓冲数组的方式，复制接近1G的文件只花费了4s的时间，效率大大提升。

2、IO流的异常处理

package pers.zzz.copy;
    
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    public class CopyDemo1 {
        public static void main(String[] args) {
            FileOutputStream fo = null;
            FileInputStream fi = null;
            long startTime = System.currentTimeMillis();
            try {
                fi = new FileInputStream("M:\\网页设1计.zip");
                fo = new FileOutputStream("M:\\网页设计11.zip");
    
                byte[] buf = new byte[1024];
                int len = 0;
    
                while ((len = fi.read(buf)) != -1) {
                    fo.write(buf, 0, len); // 将数组中的指定长度的数据写入到输出流中。
                }
            } catch (IOException e) {
                System.out.println(e.toString());
            } finally {
                if (fo != null) {
                    try {
                        fo.close();
                    } catch (IOException e) {
                        System.out.println(e.toString());
                        throw new RuntimeException();
                    }
                }
                if (fi != null) {
                    try {
                        fi.close();
                    } catch (IOException e) {
                        System.out.println(e.toString());
                        throw new RuntimeException();
    
                    }
    
                }
    
            }
            long endTime = System.currentTimeMillis();
    
            System.out.println("执行此程序用了" + (endTime - startTime) + "毫秒。");
        }
    }

![1392562-20190816211231687-990594445.png][]

转载于:https://www.cnblogs.com/zhai1997/p/11366386.html

[1392562-20190816202354544-732619518.png]: /images/20230810/4a767c8b4c9c4a9ca167da510cc135b8.png
[1392562-20190816203329623-735988080.png]: /images/20230810/a241d5451d634bafbcb7781335627dfc.png
[1392562-20190816211231687-990594445.png]: /images/20230810/d5a5e673dfeb40bbb9c4004c90b1ee13.png