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Expertise: Beginner

Nov 9, 2001

When you want to send an integer through the socket from a Java application to a C application, or your Java application needs to save some integer in the file so the C application will read it, you need to convert one integer (int type ) to 4 bytes ( array of 4 bytes ). Here is a class that does the job:

 
/** Performs conversions between integer ( long ) and 4 bytes and vice
versa. */
public class IntByteConverter{
	private int intValue;
	private byte[] byteArray;
	public final static int mask = 256;
/** IntByteConverter constructor . */
public IntByteConverter() {
	super();
	byteArray = new byte[4];
}
/** IntByteConverter constructor. */
public IntByteConverter(int theIntValue) {
	super();
	intValue = theIntValue;
	byteArray = new byte[4];
}
/** Converts 4 bytes array to the int. */
public void bytesToInt() 
{
	int temp;
	int  pMask = 1;
	intValue = 0;
	for( int i = 0; i < 4; i++ )
	{
		if( byteArray[i] < 0 )
			temp = mask+byteArray[i];
		else
			temp = byteArray[i];
		
		intValue += temp*pMask;
		pMask *= mask;
	}		
}
/** @return byte[] */
public byte[] getBytes() {
	return byteArray;
}
/** @return int */
public int getIntValue() {
	return intValue;
}
/** Converts the int to 4 bytes array. */
public void intToBytes() 
{
	int x = intValue;
	byte y = 0;
	int temp = 0;
	for( int i = 0; i < 4; i++ )
	{
		y = (byte)(x%mask);
		if( y < 0 )
		{
			byteArray[i] = (byte)(mask + y);
			temp = x-(mask+y);
		}
		else
		{
			byteArray[i] = y;
			temp = x-y;
		}
		x = temp/mask;
	}
}
/**
 * Starts the application.
 * @param args an array of command-line arguments
 */
public static void main(java.lang.String[] args) {
	IntByteConverter c = new IntByteConverter( 50 );
	c.intToBytes();
	c.printBytes();
}

public void printBytes() 
{
	for( int i = 0; i < 4; i++ )
		System.out.print( byteArray[i] + " " );
	System.out.println();
}

public void setBytes(byte[] newByteArray)
{
	byteArray = newByteArray;
}

public void setInt(int newIntValue)
{
	intValue = newIntValue;	
}

}