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How to implement own biginteger class in java?

Posted on 2011-04-19
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Last Modified: 2012-05-11
Hello experts,

Please help me to implement my own BigInteger class in java. I'm totally lost in this assignment.
I should hold the biginteger value in some array (array of bytes) in little endian, but i don't now how to do this.
If it's too difficult, implement/override the methods toString(), equals(Object obj), compareTo(BigInteger value) can be helpfull.

Thank for help

here is my demo:


public class BigInteger implements Comparable<Object> {
	
	private boolean signum; 
	
	public BigInteger(){}
	public BigInteger(long value){}
	public BigInteger(BigInteger value){}
	public BigInteger(String value){}
	
	public String toString(){
		
	}
	public boolean equals(Object obj){
		
		
	}
	public int compareTo(BigInteger value) {
		
	}
	
	public int compareTo(Object o) {
		
	}
	
	public double doubleValue(){
		
	}
	public double floatValue(){

	}
	public double intValue(){
		
	}
	public double longValue(){
		
	}
	
	
	public int getMagnitudeLength(){
		
	}
	
	public BigInteger add(BigInteger value){
		
	}
	public BigInteger add(int value){
		
	}

public static void main (String[] args){
		BigInteger c1 = new BigInteger(1234);
		System.out.println("c1 = " + c1);

		BigInteger c2 = new BigInteger(c1);
		System.out.println("c2 = " + c2);

		BigInteger c3 = new BigInteger("-456");
		System.out.println("c3 = " + c3);
		
		System.out.println("c1 == c2: " + c1.equals(c2));
		System.out.println("c1 == c3: " + c1.equals(c3));
		System.out.println("c1 ? c3: " + c1.compareTo(c3));
		
		c2 = c2.add(100).add(c1);
		System.out.println("c2 = " + c2);
 }
}

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Question by:drahos
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4 Comments
 
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Accepted Solution

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for_yan earned 2000 total points
ID: 35428105


You can use the real implementation as a reference, how to do some pieces of it:
http://developer.classpath.org/doc/java/math/BigInteger-source.html
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LVL 47

Expert Comment

by:for_yan
ID: 35428131
pay attention to this comment from the source above having to do your little-endian requirement:

 /** All integers are stored in 2's-complement form.
  63:    * If words == null, the ival is the value of this BigInteger.
  64:    * Otherwise, the first ival elements of words make the value
  65:    * of this BigInteger, stored in little-endian order, 2's-complement form. */
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LVL 86

Expert Comment

by:CEHJ
ID: 35428139
BigInteger classes are usually String-oriented. You might like to store each digit in ascii in the array beginning with the most significant digit
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LVL 86

Expert Comment

by:CEHJ
ID: 35467640
Help provided, which should be acknowledged
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