Java-IO

Posted 2021-01-11 为你编程

 1 public class Member {
 2     private String name;  
 3     private int age;  
 4     public Member() {  
 5     }  
 6    public Member(String name, int age) {  
 7         this.name = name;  
 8         this.age = age;  
 9     }  
10     public void setName(String name){  
11         this.name = name;  
12     }  
13     public void setAge(int age) {  
14         this.age = age;  
15     }  
16     public String getName() {  
17         return name;  
18     }  
19     public int getAge() {  
20         return age;  
21     }  
22 }

 1 import java.io.DataInputStream;
 2 import java.io.DataOutputStream;
 3 import java.io.FileInputStream;
 4 import java.io.FileOutputStream;
 5 import java.io.IOException;
 6 
 7 /**
 8  * DataOutputStream
 9  */
10 public class DataStreamTest {
11     public static void main(String[] args) {
12         Member[] members = { new Member("Justin", 90), 
13                              new Member("momor", 95), 
14                              new Member("Bush", 88) };
15         try {
16             DataOutputStream dos = new DataOutputStream(new FileOutputStream("E:/member.txt"));
17             for (Member member : members) {
18                 // 写入UTF字符串
19                 dos.writeUTF(member.getName());
20                 // 写入int数据
21                 dos.writeInt(member.getAge());
22             }
23             dos.flush();// 将流中的数据刷新到目的地
24             dos.close();// 关闭流
25 
26             DataInputStream dis = new DataInputStream(new FileInputStream("E:/member.txt"));
27             // 读出数据并还原为对象
28             for (int i = 0; i < members.length; i++) {
29                 String name = dis.readUTF();// 读出UTF字符串
30                 int score = dis.readInt();// 读出int数据
31                 members[i] = new Member(name, score);
32             }
33             dis.close();// 关闭流
34 
35             // 显示还原后的数据
36             for (Member member : members) {
37                 System.out.printf("%s	%d%n", member.getName(), member.getAge());
38             }
39         } catch (IOException e) {
40             e.printStackTrace();
41         }
42     }
43 }

 1 import java.io.File;
 2 import java.io.FileInputStream;
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 
 6 /**
 7  * FileInputStream  字节输入流
 8  */
 9 public class FileInputStreamTest {
10     public static void main(String[] args) {
11         InputStream in = null;//文件输入流  
12          try{  
13              in = new FileInputStream(new File("E:/fileInputStreamTest.txt"));  
14              /*
15               * FileInputStream是有缓冲区的，所以用完之后必须关闭，否则可能导致内存占满，数据丢失。 
16               */  
17              int i = 0;//接收读取的内容
18              //streamReader.read()从文件读取一个字节，并当做int类型返回，如果遇到文件末尾，则返回-1
19              while((i = in.read())!=-1) {
20                  System.out.print((char)i);//打印读取的内容
21              }  
22          }catch (final IOException e) {  
23              e.printStackTrace();  
24          }finally{  
25              try{  
26                  in.close();  //关闭流
27              }catch (IOException e) {  
28                 e.printStackTrace();  
29              }  
30          }  
31     }
32 }

 1 import java.io.FileInputStream;
 2 import java.io.FileOutputStream;
 3 import java.io.IOException;
 4 
 5 /**
 6  * 文件拷贝
 7  */
 8 public class FileCopy {
 9     public static void main(String[] args) {
10          byte[] b=new byte[512];   //一次取出的字节数大小,缓冲区大小  
11          int i=0;  
12          FileInputStream input=null;  
13          FileOutputStream out =null;  
14          try {  
15             input=new FileInputStream("E:/fileInputStreamTest.txt");  
16             out=new FileOutputStream("E:/copy.txt",true); //如果文件不存在会自动创建,true表示写在文件末尾  
17              
18             while ((i=input.read(b))!=-1) { //i的目的在于防止最后一次读取的字节小于b长度,否则会自动被填充0
19                 //使用输出流写入读取的内容到指定文件
20                out.write(b, 0, i);
21             }  
22          } catch (final IOException e) {  
23             e.printStackTrace();  
24          }finally{  
25             try {  
26                input.close();  
27                out.close();  
28             } catch (IOException e) {  
29                e.printStackTrace();  
30             }  
31          }  
32     }
33 }

 1 import java.io.BufferedReader;
 2 import java.io.BufferedWriter;
 3 import java.io.File;
 4 import java.io.FileReader;
 5 import java.io.FileWriter;
 6 import java.io.IOException;
 7 
 8 /**
 9  * BufferedReader、BufferedWriter
10  */
11 public class FileWriterTest {
12     public static void main(String[] args) throws IOException{
13         BufferedReader br = new BufferedReader(new FileReader(new File("E:/printTest.txt")));
14         BufferedWriter bw = new BufferedWriter(new FileWriter(new File("E:/writeCopy.txt")));
15         
16         String str = null;
17         try {
18             while((str = br.readLine())!=null) { //一次读一行
19                 bw.write(str);
20             }
21         } catch (IOException e) {
22             e.printStackTrace();
23         }finally {
24             br.close();
25             bw.close();
26         }
27     }
28 }

 1 import java.io.Serializable;
 2 
 3 public class Student implements Serializable{
 4     
 5     private static final long serialVersionUID = 1L;
 6     private String name;  
 7     private int age;  
 8     public Student() {}
 9     public String getName() {
10         return name;
11     }
12     public void setName(String name) {
13         this.name = name;
14     }
15     public int getAge() {
16         return age;
17     }
18     public void setAge(int age) {
19         this.age = age;
20     }
21     public Student(String name, int age) {  
22          this.name = name;  
23          this.age = age;  
24     }  
25     @Override  
26     public String toString() {  
27         return "Student [name=" + name + ", age=" + age + "]";  
28     }  
29 }

 1 import java.io.FileInputStream;
 2 import java.io.FileOutputStream;
 3 import java.io.IOException;
 4 import java.io.ObjectInputStream;
 5 import java.io.ObjectOutputStream;
 6 import java.util.ArrayList;
 7 import java.util.List;
 8 
 9 /**
10  *    ObjectOutputStream
11  */
12 public class ObjectStream {
13     public static void main(String[] args) {
14         // 对象输入输出流
15         ObjectOutputStream ow = null;
16         ObjectInputStream or = null;
17         List<Student> stuList = new ArrayList<Student>();
18         Object obj = null;
19         try {
20             // 先将对象输出到文件中
21             ow = new ObjectOutputStream(new FileOutputStream("E:/student.txt"));
22             ow.writeObject(new Student("gg", 22));
23             ow.writeObject(new Student("tt", 18));
24             ow.writeObject(new Student("rr", 17));
25             ow.writeObject(null);//添加一个null  是为了后续判断是否读取到末尾
26             // 然后从该文件读取对象
27             or = new ObjectInputStream(new FileInputStream("E:/student.txt"));
28             
29             while((obj = or.readObject())!=null) {
30                 stuList.add((Student) obj);// 将读取的对象强转成Student对象
31             }
32             for (Student student : stuList) {
33                 System.out.println(student.getName() + "-" + student.getAge());
34             }
35         } catch (IOException e) {
36             e.printStackTrace();
37         } catch (ClassNotFoundException e) {
38             e.printStackTrace();
39         } finally {
40             try {
41                 ow.close();
42                 or.close();//关闭流
43             } catch (IOException e) {
44                 e.printStackTrace();
45             }
46         }
47     }
48 }

 1 import java.io.FileReader;
 2 import java.io.IOException;
 3 import java.io.PrintWriter;
 4 
 5 /**
 6  * PrintWriter
 7  */
 8 public class PrintTest {
 9     public static void main(String[] args) {
10         FileReader reader=null;        //读取字符文件的流  
11         PrintWriter writer=null;    //写字符到控制台的流  
12         char[] b=new char[512];   //一次取出的字节数大小,缓冲区大小  
13         int i=0;  
14         try {  
15            reader=new FileReader("E:/fileInputStreamTest.txt");  
16            //writer=new PrintWriter(System.out);  //输出到控制台
17            writer=new PrintWriter("E:/printTest.txt");  //输出指定文件，没有自动创建
18            
19            while ((i = reader.read(b))!=-1) {  
20               writer.write(b, 0, i);  
21            }  
22         } catch (IOException e) {  
23            e.printStackTrace();  
24         }finally{  
25            try {  
26               reader.close();  
27            } catch (IOException e) {  
28               e.printStackTrace();  
29            }  
30            writer.close();
31         }  
32     }
33 }

 1 import java.io.ByteArrayInputStream;
 2 import java.io.IOException;
 3 import java.io.PushbackInputStream;
 4 /**
 5  * 回退流：PushbackInputStream类继承了FilterInputStream类是iputStream类的修饰者。
 6  * 提供可以将数据插入到输入流前端的能力(当然也可以做其他操作)。
 7  * 简而言之PushbackInputStream类的作用就是能够在读取缓冲区的时候提前知道下一个字节是什么，
 8  * 其实质是读取到下一个字符后回退的做法，这之间可以进行很多操作，这有点向你把读取缓冲区的过程当成一个数组的遍历，
 9  * 遍历到某个字符的时候可以进行的操作，
10  * 当然，如果要插入，能够插入的最大字节数是与推回缓冲区的大小相关的，插入字符肯定不能大于缓冲区吧！
11  */
12 public class PushBackInputStreamTest {
13     public static void main(String[] args) throws IOException {
14         String str = "hello,rollenholt";  
15         PushbackInputStream push = null; // 声明回退流对象  
16         ByteArrayInputStream bat = null; // 声明字节数组流对象  
17         bat = new ByteArrayInputStream(str.getBytes());  
18         push = new PushbackInputStream(bat); // 创建回退流对象，将拆解的字节数组流传入  
19         int temp = 0;  
20         while ((temp = push.read()) != -1) { // push.read()逐字节读取存放在temp中，如果读取完成返回-1  
21            if (temp == ‘,‘) { // 判断读取的是否是逗号
22               push.unread(temp); //回到temp的位置  
23               temp = push.read(); //接着读取字节  
24               System.out.print("(回退" + (char) temp + ") "); // 输出回退的字符  
25            } else {  
26               System.out.print((char) temp); // 否则输出字符  
27            }  
28         }  
29     }
30 }

 1 import java.io.BufferedOutputStream;
 2 import java.io.FileInputStream;
 3 import java.io.FileNotFoundException;
 4 import java.io.FileOutputStream;
 5 import java.io.IOException;
 6 import java.io.InputStream;
 7 import java.io.SequenceInputStream;
 8 import java.util.Enumeration;
 9 import java.util.Vector;
10 
11 /**
12  * SequenceInputStream
13  */
14 public class SequenceInputStreamTest {
15      /** 
16        *  SequenceInputStream合并流，
17        *   将与之相连接的流集组合成一个输入流并从第一个输入流开始读取， 
18        *   直到到达文件末尾，接着从第二个输入流读取，依次类推，直到到达包含的最后一个输入流的文件末尾为止。 
19        *   合并流的作用是将多个源合并合一个源。可接收枚举类所封闭的多个字节流对象。 
20        */  
21       public static void main(String[] args) {  
22          doSequence();  
23       }  
24       private static void doSequence() {  
25          // 创建一个合并流的对象  
26          SequenceInputStream sis = null;  
27          // 创建输出流。  
28          BufferedOutputStream bos = null;  
29          try {  
30             // 构建流集合。  
31             Vector<InputStream> vector = new Vector<InputStream>();  
32             vector.addElement(new FileInputStream("E:/text1.txt"));  
33             vector.addElement(new FileInputStream("E:/text2.txt"));  
34             vector.addElement(new FileInputStream("E:/text3.txt"));  
35             Enumeration<InputStream> e = vector.elements();  
36        
37             sis = new SequenceInputStream(e);  //将多个输入流合并到合并流
38             bos = new BufferedOutputStream(new FileOutputStream("E:/text4.txt",true));//true追加末尾
39             // 读写数据  
40             byte[] buf = new byte[1024];  
41             int len = 0;  
42             while ((len = sis.read(buf)) != -1) {  
43                bos.write(buf, 0, len);  
44                bos.flush();
45             }  
46          } catch (FileNotFoundException e1) {  
47             e1.printStackTrace();  
48          } catch (IOException e1) {  
49             e1.printStackTrace();  
50          } finally {  
51             try {  
52                if (sis != null)  
53                   sis.close();  
54             } catch (IOException e) {  
55                e.printStackTrace();  
56             }  
57             try {  
58                if (bos != null)  
59                   bos.close();  
60             } catch (IOException e) {  
61                e.printStackTrace();  
62             }  
63          }  
64       }  
65 }