RandomAccessFile readInt() in Java

readInt(): This method is available in the java.io.RandomAccessFile class of Java.

Syntax:

int java.io.RandomAccessFile.readInt() throws IOException

This method reads a signed 32-bit integer from this file. This method reads 4 bytes from the file, starting at the current file pointer.

If the bytes read, in order, are b1, b2, b3, and b4, where 0 <= b1, b2, b3, b4 <= 255,then the result is equal to:

(b1 << 24) | (b2 << 16) + (b3 << 8) + b4

This method blocks until the four bytes are read, and the end of the stream is detected, or an exception is thrown.

Parameters: NA

Returns: the next four bytes of this file, interpreted as an int.

Throws:

1. EOFException - if this file reaches the end before reading four bytes.

2. IOException - if an I/O error occurs.

Approach 1: When no exception

Java

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

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

        File file = new File("D:\\hello.txt");
        String mode = "r";
        RandomAccessFile randomAccessFile = 
                      new RandomAccessFile(file, mode);

        System.out.println(randomAccessFile.readInt());
        randomAccessFile.close();
    }
}

Output:

825373492

Approach 2: EOFException

Java

package com.RandomAccessFile;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

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

        File file = new File("D:\\hello.txt");
        String mode = "r";
        RandomAccessFile randomAccessFile =
                   new RandomAccessFile(file, mode);

        System.out.println(randomAccessFile.readInt());
        randomAccessFile.close();
    }
}

Output:

Exception in thread "main" java.io.EOFException
	at java.base/java.io.RandomAccessFile.readInt(RandomAccessFile.java:846)
	at com.RandomAccessFile.RandomAccessFilereadInt.main(RandomAccessFilereadInt.java:14)

Approach 3: IOException 

Java

package com.RandomAccessFile;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

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

        File file = new File("D:\\hello.txt");
        String mode = "r";
        RandomAccessFile randomAccessFile = 
              new RandomAccessFile(file, mode);

        randomAccessFile.close();
        System.out.println(randomAccessFile.readInt());

    }
}

Output:

Exception in thread "main" java.io.IOException: Stream Closed
	at java.base/java.io.RandomAccessFile.read0(Native Method)
	at java.base/java.io.RandomAccessFile.read(RandomAccessFile.java:368)
	at java.base/java.io.RandomAccessFile.readInt(RandomAccessFile.java:841)
	at com.RandomAccessFile.RandomAccessFilereadInt.main(RandomAccessFilereadInt.java:15)

Some other methods of RandomAccessFile

close(): This method closes this random access file stream and releases any system resources associated with the stream.

getChannel(): This method returns the unique FileChannel object associated with this file.

getFD(): This method returns the opaque file descriptor object associated with this stream.

getFilePointer(): This method returns the current offset in this file.

length(): This method returns the length of this file.

RandomAccessFile(File, String): This method creates a random access file stream to read from, and optionally to write to, the file specified by the File argument. 

RandomAccessFile(String, String): This method creates a random access file stream to read from, and optionally to write to, a file with the specified name.

read(): This method reads a byte of data from this file.

read(byte[]): This method reads up to b.length bytes of data from this file into an array of bytes.

read(byte[], int, int): This method reads up to len bytes of data from this file into an array of bytes.

readBoolean(): This method reads a single byte from the file, starting at the current file pointer.

readByte(): This method reads a signed eight-bit value from this file.

readChar(): This method reads a character from this file. This method reads two bytes from the file, starting at the current file pointer.

readDouble():  This method reads a long value, starting at the current file pointer, as if by the readLong method, and then converts that long to a double using the longBitsToDouble method in class Double.

readFloat(): This method reads an int value, starting at the current file pointer, as if by the readInt method, and then converts that int to a float using the intBitsToFloat method in class Float.

readFully(byte[]): This method reads b.length bytes from this file into the byte array, starting at the current file pointer. 

readFully(byte[], int, int): This method reads exactly the len bytes from this file into the byte array, starting at the current file pointer.

readInt(): This method reads a signed 32-bit integer from this file. This method reads 4 bytes from the file, starting at the current file pointer.

readLine(): This method reads the next line of text from this file.

readLong(): This method reads a signed 64-bit integer from this file. This method reads eight bytes from the file, starting at the current file pointer.

readShort(): This method reads a signed 16-bit number from this file. The method reads two bytes from this file, starting at the current file pointer.

readUnsignedByte(): This method reads an unsigned eight-bit number from this file. This method reads a byte from this file, starting at the current file pointer, and returns that byte.

readUnsignedShort(): This method reads an unsigned 16-bit number from this file. This method reads two bytes from the file, starting at the current file pointer.

readUTF(): This method reads in a string from this file. The string has been encoded using a modified UTF-8 format.

seek(long): This method sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.

setLength(long): This method sets the length of this file.

skipBytes(int): This method attempts to skip over n bytes of input discarding the skipped bytes.

write(byte[]): This method writes b.length bytes from the specified byte array to this file, starting at the current file pointer.

write(int): This method writes the specified byte to this file.

write(byte[], int, int): This method writes len bytes from the specified byte array starting at offset off to this file.

writeBoolean(boolean): This method writes a boolean to the file as a one-byte value.

writeByte(int): This method writes a byte to the file as a one-byte value.

writeBytes(String): This method writes the string to the file as a sequence of bytes.

writeChar(int v): This method writes a char to the file as a two-byte value, high byte first.

writeChars(String): This method writes a string to the file as a sequence of characters.

writeDouble(double): This method converts the double argument to a long using the doubleToLongBits method in class Double and then writes that long value to the file as an eight-byte quantity, high byte first.

writeFloat(float): This method converts the float argument to an int using the floatToIntBits method in class Float and then writes that int value to the file as a four-byte quantity, high byte first.

writeInt(int): This method writes an int to the file as four bytes, the high byte first.

writeLong(long): This method writes a long to the file as eight bytes, high byte first.

writeShort(int): This method writes a short to the file as two bytes, the high byte first.

writeUTF(String): This method writes a string to the file using modified UTF-8 encoding in a machine-independent manner.