Java Java类设置 1

ObjectInputStream 类反序列化以前由 ObjectOutputStream 写入的原始数据和对象。

ObjectOutputStream 和 ObjectInputStream 都被使用，因为它为对象图提供存储。
它确保它正在工作的对象与 JVM 的类（即Java虚拟机）相匹配。只有那些 Object 可以从支持Serializable或Externalizable – IO 类的流中读取，否则会出错。
Serializable 基本上是 JVM（Java虚拟机）的一种标记，指示它写出 Stream 中存在的 Object 的状态

宣言：

public class ObjectInputStream
  extends InputStream
    implements ObjectInput, ObjectStreamConstants

构造函数：

protected ObjectInputStream() ：帮助子类不分配 ObjectInputStream 使用的私有数据，如果它们正在重新实现 ObjectInputStream。
ObjectInputStream(InputStream source_input) ：创建从“source_input”输入流中读取数据的 ObjectInputStream。

方法：

read() : Java.io.ObjectInputStream.read()读取数据字节并阻塞，以防没有数据可供读取。
句法：

public int read()
Parameters : 
-----------
Return : 
reads byte else, return -1 if end of Stream is detected.
Exception :
-> IOException : in case of any IO error occurs.

readBoolean() : Java.io.ObjectInputStream.readBoolean()读入一个布尔值。
句法：

public int readBoolean()
Parameters : 
-----------
Return : 
reads in a boolean.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

// Java program explaining the working of read(), readBoolean() method
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
          
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
        ObjectInputStream Geek_inStream = 
                        new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
        // Methods covered in later
        geek_outStream.writeBoolean(true);
        geek_outStream.writeUTF("Geeks For Geeks");
        geek_outStream.flush();
  
        // Use of readBoolean() 
        System.out.println("USe of readBoolean() : " + Geek_inStream.readBoolean());
  
        System.out.print("Use of read() method in Java : ");
          
        // Use of read() method : reading the content of file
        for (int i = 0; i < Geek_inStream.available();)
        {
            System.out.print((char) Geek_inStream.read());
        }
  
    }
}

输出：

USe of readBoolean() : true
Use of read() method in Java : Geeks For Geeks

read(byte[] buffer, int offset, int maxlen) : Java.io.ObjectInputStream.read(byte[] buffer, int offset, int maxlen)从'buffer'中读取部分数据，从offset位置到maxlen位置缓冲区。
句法：

public int read(byte[] buffer, int offset, int maxlen)
Parameters : 
buffer : buffer to be read
offset : starting position of the buffer
maxlen : max. no. of bytes to be read
Return : 
reads 'maxlen' bytes of data else, return -1 if end of Stream is detected.
Exception :
-> IOException : in case of any IO error occurs.

// Java program explaining the working of
// read(byte[] buffer, int offset, int maxlen)
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
          
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
          
        // create an ObjectInputStream for the file we created before
        ObjectInputStream Geek_inStream
            = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
  
        geek_outStream.writeUTF("GeeksForGeeks");
        geek_outStream.flush();
  
        byte[] buffer = new byte[25];
  
        // Use of read(byte[] buffer, int offset, int maxlen)
        Geek_inStream.read(buffer, 2, 20);
  
        System.out.print("Use of read(buffer, offset, maxlen) : ");
        for (int i = 0; i < 19; i++)
        {
            System.out.print((char)buffer[i]);
        }
    }
}

输出：

GeeksForGeeks

readByte() : Java.io.ObjectInputStream.readByte()读取 8 位字节。
句法：

public byte readByte()
Parameters : 
-----------
Return : 
reads 8-bit byte.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readChar() : Java.io.ObjectInputStream.readChar()读取 16 位字符。
句法：

public int read()
Parameters : 
-----------
Return : 
reads 16-bit of char.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readDouble() : Java.io.ObjectInputStream.readDouble()读取 64 位双精度。
句法：

public double readDouble()
Parameters : 
-----------
Return : 
reads 64 bit double.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readFloat() : Java.io.ObjectInputStream.readFloat()读取一个 32 位浮点数。
句法：

public float readFloat()
Parameters : 
-----------
Return : 
reads a 32 bit float.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readInt() : Java.io.ObjectInputStream.readInt()读取一个 32 位整数。
句法：

public int readInt()
Parameters : 
-----------
Return : 
reads a 32 bit int.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readLong() : Java.io.ObjectInputStream.readLong()读取 64 位长。
句法：

public long readLong()
Parameters : 
-----------
Return : 
reads a 64 bit long.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

// Java program explaining the working of
// readChar(), writeByte(), writeDouble(),
// writeFloat(), writeInt(), writeLong()
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
          
        // create an ObjectInputStream for the file we created before
        ObjectInputStream Geek_inStream 
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
  
        geek_outStream.writeChar('G');
        geek_outStream.writeByte('G');
        geek_outStream.writeDouble(00436754746);
        geek_outStream.writeFloat(2.12345f);
        geek_outStream.writeInt(3576);
        geek_outStream.writeLong(368723776);
  
        geek_outStream.flush();
  
        // Use of readChar()
        System.out.println("Use of readChar() : " + Geek_inStream.readChar());
  
        // Use of readByte() :
        System.out.println("Use of readByte() : " + Geek_inStream.readByte());
  
        // Use of readDouble() :
        System.out.println("Use of readDouble() : " + Geek_inStream.readDouble());
  
        // Use of readFloat() :
        System.out.println("Use of readFloat() : " + Geek_inStream.readFloat());
  
        // Use of readInt() :
        System.out.println("Use of readInt() : " + Geek_inStream.readInt());
  
        // Use of readLong() :
        System.out.println("Use of readLong() : " + Geek_inStream.readLong());
    }
}

输出：

Use of readChar() : G
Use of readByte() : 71
Use of readDouble() : 7.5225574E7
Use of readFloat() : 2.12345
Use of readInt() : 3576
Use of readLong() : 368723776

readUnsignedByte() : Java.io.ObjectInputStream.readUnsignedByte()读取一个无符号的 8 位字节。
句法：

public int readUnsignedByte()
Parameters : 
-----------
Return : 
reads an unsigned 8 bit byte.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

readUnsignedShort() : Java.io.ObjectInputStream.readUnsignedShort()读取一个无符号的 16 位短。
句法：

public int readUnsignedShort()
Parameters : 
-----------
Return : 
reads an unsigned 16 bit short.
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if end of the stream is reached.

// Java program explaining the working of
// readUnsignedByte() and readUnsignedShort()
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
          
        // create an ObjectInputStream for the file we created before
        ObjectInputStream Geek_inStream 
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
        geek_outStream.writeByte(111);
        geek_outStream.writeShort(121212);
  
        geek_outStream.flush();
  
        // Use of readUnsignedByte()
        System.out.println("readUnsignedByte() : " 
                        + Geek_inStream.readUnsignedByte());
  
        // Use of readUnsignedShort() :
        System.out.println("readUnsignedShort() : " 
                        + Geek_inStream.readUnsignedShort());
    }
}

输出：

readUnsignedByte() : 111
readUnsignedShort() : 55676

readUTF( ) : Java.io.ObjectInputStream.readUTF()以修改后的 UTF-8（Unicode 转换格式）格式读取字符串。 UTF -8 意味着它使用 8 位块来表示一个字符。
句法：

public String readUTF()
Parameters : 
public final Object readObject()
Return : 
reads String in modified UTF-8 (Unicode Transformation Format) format
Exception :
-> IOException : in case of any IO error occurs.

// Java program explaining the working of readUTF()
  
import java.io.*;
  
public clas// Java program explaining the working of readUTF()
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException, ClassNotFoundException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
  
        ObjectInputStream Geek_inStream 
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
          
        geek_outStream.writeUTF("gEEKSArehERE");
        geek_outStream.flush();
  
        // Use of readUTF() method 
        System.out.println("Use of readUTF() : " + Geek_inStream.readUTF());
    }
}

输出：

Use of readUTF() : gEEKSArehERE

skipBytes(int maxlen) : Java.io.ObjectInputStream.skipBytes(int maxlen)跳过“maxlen”号。读取时的字节数。
句法：

public int skipBytes(int maxlen)
Parameters : 
maxlen : max. no. of bytes to be skipped
Return : 
no. of bytes to be skipped
Exception :
-> IOException : in case of any IO error occurs.

// Java program explaining the working of skipBytes()
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException, ClassNotFoundException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
  
        ObjectInputStream Geek_inStream 
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
                      
        geek_outStream.writeUTF("gEEKSArehERE");
        geek_outStream.flush();
  
        // Use of skipBytes() : 
        Geek_inStream.skipBytes(7);
          
        for (int i = 2; i < Geek_inStream.available(); i++) 
        {
            System.out.print((char) Geek_inStream.readByte());
        }
    }
}

输出：

Are

readFully(byte[] destination) : Java.io.ObjectInputStream.readFully(byte[] destination)将所有字节从源读取到目标数组。
句法：

public void readFully(byte[] destination)
Parameters : 
destination : the buffer in which the data is to be read
Return : 
returns the 32 bit float read
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if End of stream is reached

// Java program explaining the working of readFully()
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException, ClassNotFoundException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
  
        ObjectInputStream Geek_inStream
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
        geek_outStream.writeUTF("gEEKSArehERE");
        geek_outStream.flush();
  
      
       
        byte[] destination = new byte[14];
          
        // Use of readFully() 
        Geek_inStream.readFully(destination);
          
        String str = new String(destination);
        System.out.println("Use of readFully(destination, offset, maxlen) : "+str);
    }
}

输出：

Use of readFully(destination, offset, maxlen) : gEEKSArehERE

readFully(byte[] destination, int offset, int maxlen) : Java.io.ObjectInputStream.readFully(byte[] destination, int offset, int maxlen)从源读取一些字节（从偏移到 maxlen 位置）到目标大批。
句法：

public void readFully(byte[] destination, int offset, int maxlen)
Parameters : 
destination : the buffer in which the data is to be read
offset : starting position of the buffer
maxlen : max no. of bytes to be read
Return : 
void
Exception :
-> IOException : in case of any IO error occurs.
-> EOFException : if End of stream is reached

// Java program explaining the working of 
// readFully(byte[] destination, int offset, int maxlen)
  
import java.io.*;
  
public class NewClass
{
    public static void main(String[] args) throws IOException, ClassNotFoundException
    {
        // create a new file with an ObjectOutputStream and ObjectInputStream
        FileOutputStream geek_out = new FileOutputStream("GEEKS.txt");
        ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out);
  
        ObjectInputStream Geek_inStream 
                    = new ObjectInputStream(new FileInputStream("GEEKS.txt"));
  
        geek_outStream.writeUTF("gEEKSArehERE");
        geek_outStream.flush();
  
      
        byte[] destination = new byte[14];
          
        // Use of readFully(byte[] destination, int offset, int maxlen) 
        Geek_inStream.readFully(destination, 3, 7);
          
        String str = new String(destination);
        System.out.println("Use of readFully(destination, offset, maxlen) : "+ str);
    }
}

输出：

Use of readFully(destination, offset, maxlen) : geeks