Java二进制流

1-二进制流的概述

二进制流有两个顶级类：InputStream和OutputStream，下面的两个类是各种附属类。作为对比，二进制流的关系比字符流的更加多样化和复杂。关于二进制流，LineNumberInputStream和StringBufferInputStream两个类在JDK1.5中，尽量不要使用，因为它们已被弃用。

2- InputStream & OutputStream类

InputStream类是一个抽象类，所以您不能在 InputStream 类本身创建输出流对象。然而，这个类分为由关联类继承许多分支。在特定情况下，您可以从构造函数创建InputStream派生类的对象。

// Java.io.InputStream is an abstract class
// Could not initialize InputStream object directly, through class InputStream.
// Initialize InputStream object should be through its subclasses ..

InputStream fileStream =new FileInputStream("C:/test.txt");

// Input stream from the keyboard ..
InputStream is = System.in;

OutputStream类是一个抽象类，所以你无法通过的OutputStream类来创建输出流对象。然而，这个类分割成子分支发挥了重要作用。在某些情况下，您可以从子类的构造函数创建InputStream对象。

// Java.io.OutputStream is an abstract class
// Could not initialize OutputStream object directly, through class OutputStream.
// Initialize OutputStream object should be through its subclasses ..

// Stream write to file.
OutputStream os=new FileOutputStream("D:/outData.txt");

// Stream write to console.
OutputStream w=System.out;

HelloInputStream.java

package com.yiibai.tutorial.javaio.stream;

import java.io.FileInputStream;
import java.io.InputStream;

public class HelloInputStream {

    public static void main(String[] args) {
        try {
       
            // Create InputStream object from subclass.
            // This is Stream read file.
            InputStream is = new FileInputStream("data.txt");

            int i = -1;
           
            // Read the turn of bytes in the stream.
            // Each time the 8-bit read, convert it to int.
            // Read the value of -1 means the end of the stream.
            while ((i = is.read()) != -1) {
                System.out.println(i + "  " + (char) i);
            }
            is.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

输出结果如下：

HelloOutputStream.java

package com.yiibai.tutorial.javaio.stream;

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

public class HelloOutputStream {

   public static void main(String[] args) {
       try {
           File dir = new File("C:/Test");

           // Create directories if not exists
           dir.mkdirs();

           // Create output Stream write data to file.
           OutputStream w = new FileOutputStream(
                   "C:/Test/test_outputStream.txt");
           
           // Create array of bytes, write it to stream.
           byte[] by = new byte[] { 'H', 'e', 'l', 'l', 'o' };

           // write turn the bytes into the stream
           for (int i = 0; i < by.length; i++) {
               byte b = by[i];

               // Write 1 byte.
               w.write(b);
           }
           // Close the output stream, finish write file.
           w.close();
       } catch (Exception e) {
           e.printStackTrace();
       }
   }
}

输出结果如下：

以上两个例子是简单的。以上两个例子是简单的。它们读或写每个字节。在下面的例子中，它们读或写同步不同的字节。这有助于提高处理速度。

InputStreamExample2.java

package com.yiibai.tutorial.javaio.stream;

import java.io.FileInputStream;
import java.io.InputStream;

public class InputStreamExample2 {

    public static void main(String[] args) {
        try {

            // Create input stream, read a file.
            InputStream in = new FileInputStream("data.txt");

            // A temporary array to store data each reading
            byte[] temp = new byte[10];
            int i = -1;

           
            // Reads some number of bytes from the input stream
            // and stores them into the buffer array 'temp'.
            // Return the number of bytes actually read.
            // return -1 if end of stream.
            while ((i = in.read(temp)) != -1) {

                // Create String from bytes
                String s = new String(temp, 0, i);
                System.out.println(s);
            }
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

在下面图片的例子中说明了同时进行读取：

OutputStreamExample2.java

package com.yiibai.tutorial.javaio.stream;

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

public class OutputStreamExample2 {

    public static void main(String[] args) {
        try {
            File dir = new File("C:/Test");

            // Create directories if not exists.
            dir.mkdirs();            
            
            // Create output Stream to write file.
            OutputStream os = new FileOutputStream("C:/Test/test_writerOutputStream.txt");
            
            // Create array of bytes, write bytes into the file above.
            byte[] by = new byte[] { 'H', 'e', 'l', 'l', 'o', ' ', 31, 34, 92 };
            byte[] by2 = new byte[] { 'H', 'e', 'l', 'l', 'o', ' ', 'b', 'o',
                    'y' };
            
            // Write all of bytes in array into Stream.
            os.write(by);
            
            // Flush data in memory to file.
            os.flush();
            
            // Continue write the 2nd byte array to the stream
            os.write(by2);
            
            // Close the output stream, finish write file.
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3- ByteArrayInputStream & ByteArrayOutputStream类

ByteArrayInputStream包装字节数组（byte[] buf），并通过ByteArrayInputStream进行访问数组的元素。

ByteArrayOutputStream是一个字节流，其中包含的一个的数组字节流(byte[]buf) 能够通过自身数量的增加，以增加字节的大小。每个字节每次被写入流时，这意味着分配这些字节到的数组。

当数组是充分分配元素，程序创建旧数组在一个新较长数组并拷贝元素为...（这是它自己的增加的字节数组的大小 - 如上所述）

ByteArrayOutputStream的一些方法：

// return the current contents of this output stream, as a byte array.
  - byte[] toByteArray();

// String decoded from the buffer's contents.
  - String toString() ;

// return the number of valid bytes in this output stream.
  - int size();

ByteArrayInputStreamExample.java

package com.yiibai.tutorial.javaio.bytestream;

import java.io.ByteArrayInputStream;
import java.io.IOException;

public class ByteArrayInputStreamExample {

    public static void main(String args[]) throws IOException {

        // Byte Array.
        byte[] bytes = new byte[] { 'H', 'e', 'l', 'l', 'o', ' ', 'I', 'O' };

        // Using ByteArrayInputStream to read bytes array.
        ByteArrayInputStream bInput = new ByteArrayInputStream(bytes);

        System.out.println("Converting characters to Upper case ");
        int c = 0;

        // Read the turn of bytes in the stream.
        // Cursor will move from the beginning to the end of the array array.
        // Every time you read a byte pointer will move one step to the end.        
        while ((c = bInput.read()) != -1) {
            char ch = (char) c;
            ch = Character.toUpperCase(ch);
            System.out.println(ch);
        }

        // Check whether this stream supports mark or not
        boolean markSupport = bInput.markSupported();

        System.out.println("Mark Support? " + markSupport);
       
        // Move the cursor to the default location
        // In this example, it will move to position 0 ..        
        bInput.reset();

        char ch = (char) bInput.read();
        System.out.println(ch);

         // Read next byte
        ch = (char) bInput.read();
        System.out.println(ch);

        System.out.println("Skip 4");
 
        // Skip 4 bytes
        bInput.skip(4);
        ch = (char) bInput.read();
        System.out.println(ch);

    }

}

输出结果：

ByteArrayOutputStreamExample.java

package com.yiibai.tutorial.javaio.bytestream;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class ByteArrayOutputStreamExample {

    public static void main(String args[]) throws IOException {


        // Create ByteArrayOutputStream object.
        // Object contains within it an array of bytes.
        // Array with size 12 elements.
        // If the number of elements to write to stream more than 12, the array will be replaced by
        // new array has more elements, and copy the elements of old array into.        
        ByteArrayOutputStream bOutput = new ByteArrayOutputStream(12);

        String s = "Hello ByteArrayOutputStream";

        for (int i = 0; i < s.length(); i++) {

            char ch = s.charAt(i);

            if (ch != 'a' && ch != 'e') {
                bOutput.write(ch);
            }
        }

        // Returns the current size of the buffer.
        int size = bOutput.size();
        System.out.println("Size = " + size);

        byte[] bytes = bOutput.toByteArray();

        String ss = new String(bytes);

        System.out.println("New String = " + ss);
    }
}

输出结果：

4- ObjectInputStream和ObjectOutputStream类

ObjectInputStream和ObjectOutputStream，并允许您对读取或写入流中。这些对象必须是可序列化的类型(这意味着它们可布置成队列)。

这里有些例子：

Student.java

package com.yiibai.tutorial.javaio.objstream;

import java.io.Serializable;

public class Student implements Serializable {
 
    private static final long serialVersionUID = -5074534753977873204L;

    private String firstName;

    private String lastName;

    public Student(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

}

Pupil.java

package com.yiibai.tutorial.javaio.objstream;

import java.io.Serializable;

public class Pupil implements Serializable {
   
    private static final long serialVersionUID = -8501383434011302991L;
    
    private String fullName;

    public Pupil(String fullName)  {
        this.fullName= fullName;
    }
    
    public String getFullName() {
        return fullName;
    }

    public void setFullName(String fullName) {
        this.fullName = fullName;
    }

}

ObjectOutputStreamExample.java

package com.yiibai.tutorial.javaio.objstream;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.Date;

public class ObjectOutputStreamExample {

    public static void main(String[] args) throws IOException {
        File dir = new File("C:/Test");

        // Create directories if not exists.
        dir.mkdirs();


        // Create stream write to file.
        FileOutputStream fos = new FileOutputStream(
                "C:/Test/testObjectStream.txt");

       
        // Create ObjectOutputStream object wrap 'fos'.
        // Data written to this stream will be pushed to 'fos'.
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        
        
        // Write String to Stream.
        oos.writeUTF("This is student, pupil profiles");
    
  
        // Note: Write Serializable object only.
        // Write an Object to stream.
        oos.writeObject(new Date());

        Student student1 = new Student("Thanh", "Phan");
        Student student2 = new Student("Ngan", "Tran");
        Pupil pupil1 = new Pupil("Nguyen Van Ba");

        oos.writeObject(student1);
        oos.writeObject(pupil1);
        oos.writeObject(student2);

        oos.close();
        System.out.println("Write successful");
    }

}

运行结果：

这是一个关于文件写入对象的图示。它被依次处理。在未来阅读时，你要记住写这样可以读取它正确的顺序。

这是上述实例中提到的 ObjectInputStream EOF 读取文件的一个例子：

ObjectInputStreamExample.java

package com.yiibai.tutorial.javaio.objstream;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Date;

public class ObjectInputStreamExample {

    public static void main(String[] args) throws IOException,
            ClassNotFoundException {

        // Create stream to read file.
        FileInputStream fis = new FileInputStream(
                "C:/Test/testObjectStream.txt");

        // Create ObjectInputStream object wrap 'fis'.
        ObjectInputStream ois = new ObjectInputStream(fis);

        // Read String.
        String s = ois.readUTF();

        System.out.println(s);

        // Read Object.
        Date date = (Date) ois.readObject();
        System.out.println("Date = " + date);

        Student student1 = (Student) ois.readObject();

        System.out.println("Student " + student1.getFirstName());

        Pupil pupil = (Pupil) ois.readObject();

        System.out.println("Pupil " + pupil.getFullName());

        Student student2 = (Student) ois.readObject();

        System.out.println("Student " + student2.getFirstName());

        ois.close();
    }
}

运行结果：

5- Class DataInputStream 和 DataOutputStream

DataInputStream

// Constructor
public DataOutputStream(OutputStream out)

// Write a character 16 bit (2-byte)
public void writeChar(int val)
// Write double 64 bit (8-byte)
public void writeDouble(double val)
// Write float 32 bit (4-byte)
public void writeFloat(float val)
// Write integer 32 bit (4-byte)
public void writeInt(int val)
// Write String UTF-8.
public void writeUTF(String obj)
....

DataInputStream

// Constructor
public DataInputStream(InputStream in)

// Read a character 16 bit (2 byte)
public char readChar()
// Read double 64 bit (8 byte)
public double readDouble()
// Read float 32 bit (4 byte)
public float readFloat()
// Read int 16 bit (4 byte)
public int readInt()
// Read UTF-8 String.
public String readUTF()
....

DataOutputStreamExample.java

package com.yiibai.tutorial.javaio.datastream;

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class DataOutputStreamExample {

    public static void main(String[] args) throws IOException {
        int cityIdA = 1;
        String cityNameA = "Green Lake City";
        int cityPopulationA = 500000;
        float cityTempA = 15.50f;

        int cityIdB = 2;
        String cityNameB = "Salt Lake City";
        int cityPopulationB = 250000;
        float cityTempB = 10.45f;

        File dir = new File("C:/Test");
        dir.mkdirs();

        //
        // Create FileOutputStream write to file.
        //
        FileOutputStream fos = new FileOutputStream("C:/Test/cities.txt");

        // Create DataOutputStream object wrap 'fos'.
        // The data write to 'dos' will be pushed to 'fos'.
        DataOutputStream dos = new DataOutputStream(fos);

        //
        // Write data.
        //
        dos.writeInt(cityIdA);
        dos.writeUTF(cityNameA);
        dos.writeInt(cityPopulationA);
        dos.writeFloat(cityTempA);

        dos.writeInt(cityIdB);
        dos.writeUTF(cityNameB);
        dos.writeInt(cityPopulationB);
        dos.writeFloat(cityTempB);

        dos.flush();
        dos.close();
    }

}

运行 DataOutputStream 类实例类，并收到一个写出来数据文件。

DataInputStreamExample.java

package com.yiibai.tutorial.javaio.datastream;

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DataInputStreamExample {
    
    
    
    public static void main(String[] args) throws IOException {
        
         // Stream to read file.
         FileInputStream fis = new FileInputStream("C:/Test/cities.txt");

         // Create DataInputStream object wrap 'fis'.
         DataInputStream dis = new DataInputStream(fis);

         //
         // Read data.
         //
         int cityId1 = dis.readInt();
         System.out.println("Id: " + cityId1);
         String cityName1 = dis.readUTF();
         System.out.println("Name: " + cityName1);
         int cityPopulation1 = dis.readInt();
         System.out.println("Population: " + cityPopulation1);
         float cityTemperature1 = dis.readFloat();
         System.out.println("Temperature: " + cityTemperature1);

         //
         // Read data.
         //
         int cityId2 = dis.readInt();
         System.out.println("Id: " + cityId2);
         String cityName2 = dis.readUTF();
         System.out.println("Name: " + cityName2);
         int cityPopulation2 = dis.readInt();
         System.out.println("Population: " + cityPopulation2);
         float cityTemperature2 = dis.readFloat();
         System.out.println("Temperature: " + cityTemperature2);
         
         dis.close();
    }
}

运行结果：

6- SequenceInputStream

现在你已经熟悉了读取一个文件，并知道如何得到一个输入流。然而，你有时需要读取很多文件并加入数据写入另一个文件中，例如。这意味着你以串联小数据流方式，加入许多输入流在一起用来创建一个更大的流。我们现在讨论 java.io.SequenceInputStream 中的类。没有对应的定义输出流...

// Constructor

 // Create new Stream from Pairing two streams together
// which will be read in order
public SequenceInputStream(InputStream s1,InputStream s2)  
 
// Create new Stream from Multi input stream.
// which will be read in order
  public SequenceInputStream(Enumeration<? extends InputStream> e)

示例：

// Input stream read a file - File1.txt .
InputStream is1=new FileInputStream("File1.txt");
// Input stram read a file - File2.txt  
InputStream is2=new FileInputStream("File2.txt");

// Create new Stream from two stream
SequenceInputStream sis=new SequenceInputStream(is1,is2);

7- PipedInputStream,PipedOutputStream

8- Class PrintStream

// PrintStream is the subclass of FilterOutputStream.
// It can wrap a binary output stream (OutputStream) , ..
// Constructor :

   // Wrap a OutputStream
   public PrintStream(OutputStream out)

   public PrintStream(OutputStream out,boolean autoFlush)

   // Write to file ..
   public PrintStream(String fileName)
 

// Some methods
   public void println(String s)
   public void print(char ch)

   // Write an Object
   public void print(Object obj)

   // Write long value (64bit)
   public void print(long n)

   public PrintStream append(java.lang.CharSequence csq) .
   // ... (more see javadoc)

现在我们已经知道如何通过 try-catch 捕捉异常。

try {    
 // Do something here
 // Error divided by 0
 int i=10/0;
}
// The catch block is executed
catch(Exception e) {  
 // Print out message
 System.out.println("Error on try..."+e.getMessage());
 // Print 'stack trace' to Console.
 // How to get the text "stack trace"?
 e.printStackTrace();
}

这是你经常看到的“堆栈跟踪”，当有东西出错时。

下面的示例是用来检索字符串“堆栈跟踪”

GetStackTraceString.java

package com.yiibai.tutorial.javaio.printstream;

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

public class GetStackTraceString {

  private static String getStackTraceString(Exception e) {
 
      // Create ByteArrayOutputStream
      ByteArrayOutputStream baos = new ByteArrayOutputStream();


      // Data written to this stream will be pushed to 'baos'.
      PrintStream printStream = new PrintStream(baos);


      // Prints this throwable and its backtrace to 'printStream'
      e.printStackTrace(printStream);

      printStream.close();
     
      byte[] bytes = baos.toByteArray();

      String s = new String(bytes);
      return s;
  }

  public static void main(String[] args) {

      try {
          // Do something here
          // Error divided by 0
          int i = 10 / 0;
      }
      // The catch block is executed
      catch (Exception e) {
          // Print out message
          System.out.println("Error on try..." + e.getMessage());

          // Get the text "stack trace"
          String s = getStackTraceString(e);

          System.out.println("Stack Trace String " + s);
      }
  }
}

下面是打印“堆栈跟踪”到控制台的代码，但使用printStackTrace(PrintStream)方法，而不是使用printStackTrace()方法，默认为打印“堆栈跟踪”到控制台。

// PrintStream to write to the Console
PrintStream os = System.out;
// Exception e ..
// Write 'stack trace' to 'os'. This means print to the Console.
e.printStackTrace(os);

// In essence it is equivalent to calling:
e.printStackTrace();

上一篇： Eclipse安装和配置下一篇：简单Java程序

易百教程

1-二进制流的概述

2- InputStream & OutputStream类

3- ByteArrayInputStream & ByteArrayOutputStream类

4- ObjectInputStream和ObjectOutputStream类

5- Class DataInputStream 和 DataOutputStream

6- SequenceInputStream

7- PipedInputStream,PipedOutputStream

8- Class PrintStream

随机教程

1-二进制流的概述

2- InputStream & OutputStream类

3- ByteArrayInputStream & ByteArrayOutputStream类

4- ObjectInputStream和ObjectOutputStream类

5- Class DataInputStream 和 DataOutputStream

6- SequenceInputStream

7- PipedInputStream,PipedOutputStream

8- Class PrintStream

随机教程

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