java中二进制流的应用

ゝ一世哀愁。 2022-05-11 03:24 165阅读 0赞

# java中二进制流的应用 #

[https://blog.csdn.net/qq\_36494506/article/details/78178224][https_blog.csdn.net_qq_36494506_article_details_78178224]

## 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;

![1-16032613395b46.png][]

*  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：  
![1-160326133R4X9.png][]

*  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：  
![1-160326134215X2.png][]

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：  
![1-1603261342444Q.png][]

*  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：  
![1-160326135155616.png][]

*  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：  
![1-160326135321561.png][]

## 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：  
![1-160326135F64P.png][]

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。  
![1-160326135I0J7.png][]

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：  
![1-160326135UQ09.png][]

## 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：  
![1-16032614014V08.png][]

## 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...  
![1-1603261402121B.png][]

// 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 ##

![1-16032614025c51.png][]  
![1-160326140322912.png][]

## 8- Class PrintStream   ![1-160326140346395.png][] ##

// 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();

[https_blog.csdn.net_qq_36494506_article_details_78178224]: https://blog.csdn.net/qq_36494506/article/details/78178224
[1-16032613395b46.png]: /images/20220511/6523a43df64342209b8922d704783617.png
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