Java入门——day29 - 戈瑾

一、今日学习

综合实例：写一个工具类，实现读写文件和复制文件等功能。
  1 package helloworld;
  2 import java.io.*;
  3 public class IOUtils {
  4     public static void main(String[] args) {
  5         byte[] ary= {41,4,-2,(byte)0xfe,(byte)0xff};
  6         for(int b:ary) {
  7             b&=0xff;
  8             if(b<=0xf)
  9                 System.out.print("0");
 10             System.out.print(Integer.toHexString(b)+" ");
 11         }
 12         System.out.println();
 13     }
 14     public static byte[] read(String file) {
 15         try {
 16             InputStream in=new FileInputStream(file);
 17             byte[] buf=new byte[in.available()];
 18             in.read(buf);
 19             in.close();
 20             return buf;
 21         }catch(IOException e) {
 22             e.printStackTrace();
 23             throw new RuntimeException(e);
 24         }
 25     }
 26     public static Object deepCopy(Object obj) {
 27         try {
 28             ByteArrayOutputStream buf=new ByteArrayOutputStream();
 29             ObjectOutputStream oos=new ObjectOutputStream(buf);
 30             oos.writeObject(obj);
 31             oos.close();
 32             byte[] ary=buf.toByteArray();
 33             ObjectInputStream ois=new ObjectInputStream(new ByteArrayInputStream(ary));
 34             Object o=ois.readObject();
 35             ois.close();
 36             return o;
 37         }catch(Exception e) {
 38             throw new RuntimeException(e);
 39         }
 40     }
 41     public static void cp(File from,File to) {
 42         try {
 43             InputStream in=new FileInputStream(from);
 44             OutputStream out=new FileOutputStream(to);
 45             byte[] buf=new byte[1024];
 46             int n;
 47             while((n=in.read(buf))!=-1) {
 48                 out.write(buf,0,n);
 49             }
 50             in.close();
 51             out.close();
 52         }catch(IOException e) {
 53             e.printStackTrace();
 54             throw new RuntimeException(e);
 55         }
 56     }
 57     public static void cpl(File from,File to) {
 58         try {
 59             InputStream in=new FileInputStream(from);
 60             OutputStream out=new FileOutputStream(to);
 61             int b;
 62             while((b=in.read())!=-1) {
 63                 out.write(b);
 64             }
 65             in.close();
 66             out.close();
 67         }catch(IOException e) {
 68             e.printStackTrace();
 69             throw new RuntimeException(e);
 70         }
 71     }
 72     public static void cp(String from,String to) {
 73         cp(new File(from),new File(to));
 74     }
 75     /**将文件按照16进制形式打印到控制台，每16个byte为一行*/
 76     public static void print(File file) {
 77         try {
 78             InputStream in=new FileInputStream(file);
 79             int b;
 80             int i=1;
 81             while((b=in.read())!=-1) {
 82                 if(b<=0xf)
 83                     System.out.print("0");
 84                 System.out.print(Integer.toHexString(b)+" ");
 85                 if(i++%16==0) {
 86                     System.out.println();
 87                 }
 88             }
 89             System.out.println();
 90             in.close();
 91         }catch(IOException e) {
 92             e.printStackTrace();
 93             throw new RuntimeException(e);
 94         }
 95     }
 96     public static void print(String file) {
 97         print(new File(file));
 98     }
 99     public static void split(String file,int size) {
100         try {
101             if(size<=0) {
102                 throw new IllegalArgumentException("搞啥呀！");
103             }
104             int idx=0;
105             InputStream in=new BufferedInputStream(new FileInputStream(file));
106             OutputStream out=new BufferedOutputStream(new FileOutputStream(file+"."+idx++));
107             int b;
108             int count=0;
109             while((b=in.read())!=-1) {
110                 out.write(b);
111                 count++;
112                 if(count%(size*1024)==0) {
113                     out.close();
114                     out=new BufferedOutputStream(new FileOutputStream(file+"."+idx++));
115                 }
116             }
117             in.close();
118             out.close();
119         }catch(IOException e) {
120             e.printStackTrace();
121             throw new RuntimeException(e);
122         }
123     }
124     public static void join(String file) {
125         try {
126             String filename=file.substring(0,file.lastIndexOf("."));
127             String num=file.substring(file.lastIndexOf(".")+1);
128             int idx=Integer.parseInt(num);
129             OutputStream out=new FileOutputStream(filename);
130             File f=new File(filename+"."+idx++);
131             while(f.exists()) {
132                 InputStream in=new FileInputStream(f);
133                 cp(in,out);
134                 in.close();
135                 f=new File(filename+"."+idx++);
136             }
137             out.close();
138         }catch(IOException e) {
139             e.printStackTrace();
140             throw new RuntimeException(e);
141         }
142     }
143     public static void cp(InputStream in,OutputStream out) throws IOException{
144         byte[] buf=new byte[1024*512];
145         int count;
146         while((count=in.read(buf))!=-1) {
147             out.write(buf,0,count);
148         }
149         out.flush();
150     }
151 }
二、遇到问题

三、明日学习

用Java语言完成C++例题
posted on 2020-08-03 21:18 戈瑾阅读(165) 评论(0) 收藏举报
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