Java.io.RandomAccessFile 类方法 |设置 1

Java.io.RandomAccessFile类提供了一种使用读写操作随机访问文件的方法。它的工作方式类似于存储在文件中的字节数组。
宣言：

public class RandomAccessFile
   extends Object
      implements DataOutput, DataInput, Closeable

RandomAccessFile 类的方法：

read() : Java.io.RandomAccessFile.read()从文件中读取数据字节。字节以 0-255 范围内的整数形式返回

Syntax :
public int read()
Parameters : 
--------
Return  :
reads byte of data from file, -1 if end of file is reached.

read(byte[] b) Java.io.RandomAccessFile.read(byte[] b)从缓冲区中读取最多 b.length 个字节。

Syntax :
public int read(byte[] b)
Parameters : 
b : buffer to be read
Return  :
byte of data from file upto b.length, -1 if end of file is reached.

read((byte[] b, int offset, int len) : Java.io.RandomAccessFile.read((byte[] b, int offset, int len)从缓冲区读取从偏移位置初始化到 b.length 的字节。

Syntax :
public int read(byte[] b, int offset, int len)
Parameters : 
b : buffer to read
offset : starting position to read
len : max no of bytes to read
Return  :
reads bytes initialising from offset position upto b.length from the buffer.

readBoolean() : Java.io.RandomAccessFile.readBoolean()从文件中读取一个布尔值。

Syntax :
public final boolean readBoolean()
Parameters : 
------
Return  :
boolean value

readByte() : Java.io.RandomAccessFile.readByte()从文件中读取一个有符号的八位值，从文件指针开始读取。
```
Syntax :
public final byte readByte()
Parameters : 
-------
Return  :
signed eight-bit value from file
```
readChar() : Java.io.RandomAccessFile.readChar()从文件中读取一个字符，从文件指针开始读取。
```
Syntax :
public final char readChar()
Parameters : 
-------
Return  :
character from the file.
```
readDouble() : Java.io.RandomAccessFile.readDouble()从文件中读取一个双精度值，从文件指针开始读取。
```
Syntax :
public final double readDouble()
Parameters : 
------
Return  :
reads a double value from the file.
```
readFloat() : Java.io.RandomAccessFile.readFloat()从文件中读取一个浮点值，从文件指针开始读取。
```
Syntax :
public final double readFloat()
Parameters : 
------
Return  :
reads a float value from the file.
```

readFully(byte[] b) : Java.io.RandomAccessFile.readFully(byte[] b)从缓冲区读取最多 b.length 的字节，从文件指针开始读取。

Syntax :
public final void readFully(byte[] b)
Parameters : 
b : buffer to be read
Return  :
reads bytes initialising from offset position upto b.length from the buffer

readInt() : Java.io.RandomAccessFile.readInt()从文件中读取一个有符号的 4 字节整数，从文件指针开始读取。

Syntax :
reads a signed 4 bytes integer from the file
Parameters : 
-----
Return  :
reads a signed 4 bytes integer from the file

readFully(byte[] b, int offset, int len) : Java.io.RandomAccessFile.readFully(byte[] b, int offset, int len)从缓冲区读取从偏移位置到 b.length 初始化的字节，从文件指针。

Syntax :
public final void readFully(byte[] b, int offset, int len)
Parameters : 
b : buffer to read
offset : starting position to read
len : max no of bytes to read
Return  :
bytes initialising from offset position upto b.length from the buffer

readLong() : Java.io.RandomAccessFile.readLong()从文件中读取一个有符号的 64 位整数，从文件指针开始读取。

Syntax :
public final long readLong()
Parameters : 
-------
Return  :
signed 64 bit integer from the file

// Java Program illustrating use of io.RandomAccessFile class methods
// read(), read(byte[] b), readBoolean(), readByte(), readInt()
// readFully(byte[] b, int off, int len), readFully(), readFloat()
// readChar(), readDouble(),
  
import java.io.*;
public class NewClass
{
    public static void main(String[] args)
    {
        try
        {
            double d = 1.5;
            float f = 14.56f;
  
            // Creating a new RandomAccessFile - "GEEK"
            RandomAccessFile geek = new RandomAccessFile("GEEK.txt", "rw");
  
            // Writing to file
            geek.writeUTF("Hello Geeks For Geeks");
  
            // File Pointer at index position - 0
            geek.seek(0);
  
            // read() method :
            System.out.println("Use of read() method : " + geek.read());
  
            geek.seek(0);
  
            byte[] b = {1, 2, 3};
              
            // Use of .read(byte[] b) method :
            System.out.println("Use of .read(byte[] b) : " + geek.read(b));
  
            // readBoolean() method :
            System.out.println("Use of readBoolean() : " + geek.readBoolean());
  
            // readByte() method :
            System.out.println("Use of readByte() : " + geek.readByte());
  
            geek.writeChar('c');
            geek.seek(0);
  
            // readChar() :
            System.out.println("Use of readChar() : " + geek.readChar());
  
            geek.seek(0);
            geek.writeDouble(d);
            geek.seek(0);
  
            // read double
            System.out.println("Use of readDouble() : " + geek.readDouble());
  
            geek.seek(0);
            geek.writeFloat(f);
            geek.seek(0);
  
            // readFloat() :
            System.out.println("Use of readFloat() : " + geek.readFloat());
  
            geek.seek(0);
            // Create array upto geek.length
            byte[] arr = new byte[(int) geek.length()];
            // readFully() :
            geek.readFully(arr);
              
            String str1 = new String(arr);
            System.out.println("Use of readFully() : " + str1);
  
            geek.seek(0);
              
            // readFully(byte[] b, int off, int len) :
            geek.readFully(arr, 0, 8);
              
            String str2 = new String(arr);
            System.out.println("Use of readFully(byte[] b, int off, int len) : " + str2);
        }
        catch (IOException ex)
        {
            System.out.println("Something went Wrong");
            ex.printStackTrace();
        }
    }
}

输出：

Use of read() method : 0
Use of .read(byte[] b) : 3
Use of readBoolean() : true
Use of readByte() : 108
Use of readChar() : c
Use of readDouble() : 1.5
Use of readFloat() : 14.56
Use of readFully() : Geeks For Geeks
Use of readFully(byte[] b, int off, int len) : Geeks For Geeks

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