java.math.BigIn teger

[shana07]

I don't understand about this program is doing. Could someone please tell me what it is about. Because I have gcd function in one program that calls this function. Thanks a lot

 
switch (opcode) {
case GCD:       out = b1.gcd(b2).toString();
                            break;

/**
     * Returns a BigInteger whose value is the greatest common divisor of
     * <tt>abs(this)</tt> and <tt>abs(val)</tt>.  Returns 0 if
     * <tt>this==0 &amp;&amp; val==0</tt>.
     *
     * @param  val value with with the GCD is to be computed.
     * @return <tt>GCD(abs(this), abs(val))</tt>
     */
    public BigInteger gcd(BigInteger val) {
        if (val.signum == 0)
        return this.abs();
    else if (this.signum == 0)
        return val.abs();
 
        MutableBigInteger a = new MutableBigInteger(this);
        MutableBigInteger b = new MutableBigInteger(val);
 
        MutableBigInteger result = a.hybridGCD(b);
 
        return new BigInteger(result, 1);
    }

[r035198x]

I don't understand about this program is doing. Could someone please tell me what it is about. Because I have gcd function in one program that calls this function. Thanks a lot

 
switch (opcode) {
case GCD: out = b1.gcd(b2).toString();
break;

/**
* Returns a BigInteger whose value is the greatest common divisor of
* <tt>abs(this)</tt> and <tt>abs(val)</tt>. Returns 0 if
* <tt>this==0 &amp;&amp; val==0</tt>.
*
* @param val value with with the GCD is to be computed.
* @return <tt>GCD(abs(this), abs(val))</tt>
*/
public BigInteger gcd(BigInteger val) {
if (val.signum == 0)
     return this.abs();
    else if (this.signum == 0)
     return val.abs();
 
MutableBigInteger a = new MutableBigInteger(this);
MutableBigInteger b = new MutableBigInteger(val);
 
MutableBigInteger result = a.hybridGCD(b);
 
return new BigInteger(result, 1);
}

which part specifically do you not understand?

[shana07]

which part specifically do you not understand?

The java package code. From my reading, signum is either '+', '-' or 0.
Then, mutableBigInteg er is for what?
As for gcd (a, b) calculation actually is about
a.gcd(b)
Then it involves with operator 'mod' to get remainder.
Where can I check those operators?

public BigInteger gcd(BigInteger val) {
if (val.signum == 0)
     return this.abs();
    else if (this.signum == 0)
     return val.abs();
 
MutableBigInteger a = new MutableBigInteger(this);
MutableBigInteger b = new MutableBigInteger(val);
 
MutableBigInteger result = a.hybridGCD(b);
 
return new BigInteger(result, 1);
}

[r035198x]

The java package code. From my reading, signum is either '+', '-' or 0.
Then, mutableBigInteg er is for what?
As for gcd (a, b) calculation actually is about
a.gcd(b)
Then it involves with operator 'mod' to get remainder.
Where can I check those operators?

public BigInteger gcd(BigInteger val) {
if (val.signum == 0)
     return this.abs();
    else if (this.signum == 0)
     return val.abs();
 
MutableBigInteger a = new MutableBigInteger(this);
MutableBigInteger b = new MutableBigInteger(val);
 
MutableBigInteger result = a.hybridGCD(b);
 
return new BigInteger(result, 1);
}

MutableBigInteg er is another class in the java.math package. It's implementation of hybridGCD is

 
MutableBigInteger hybridGCD(MutableBigInteger b) {
        // Use Euclid's algorithm until the numbers are approximately the
        // same length, then use the binary GCD algorithm to find the GCD.
        MutableBigInteger a = this;
        MutableBigInteger q = new MutableBigInteger(),
                          r = new MutableBigInteger();
        while (b.intLen != 0) {
            if (Math.abs(a.intLen - b.intLen) < 2)
                return a.binaryGCD(b);
            a.divide(b, q, r);
            MutableBigInteger swapper = a;
            a = b; b = r; r = swapper;
        }
        return a;
    }
 

[shana07]

MutableBigInteg er is another class in the java.math package. It's implementation of hybridGCD is

 
MutableBigInteger hybridGCD(MutableBigInteger b) {
        // Use Euclid's algorithm until the numbers are approximately the
        // same length, then use the binary GCD algorithm to find the GCD.
        MutableBigInteger a = this;
        MutableBigInteger q = new MutableBigInteger(),
                          r = new MutableBigInteger();
        while (b.intLen != 0) {
            if (Math.abs(a.intLen - b.intLen) < 2)
                return a.binaryGCD(b);
            a.divide(b, q, r);
            MutableBigInteger swapper = a;
            a = b; b = r; r = swapper;
        }
        return a;
    }
 

Oh it's there...alright . TQ
One more question I need to consult you.Is it possible for me to replace any operators inside this class (only gcd subroutines)? Seems I can't do mutation on my program (that calls gcd class) .
* Aim - to do mutation to this gcd function. Because I remember last time, I tried on other java default pakcages and from netbean I can't open that package anymore once I changed it (unzipped the packages and zipped back).....sorry If this confusing you....

[r035198x]

Oh it's there...alright . TQ
One more question I need to consult you.Is it possible for me to replace any operators inside this class (only gcd subroutines)? Seems I can't do mutation on my program (that calls gcd class) .
* Aim - to do mutation to this gcd function. Because I remember last time, I tried on other java default pakcages and from netbean I can't open that package anymore once I changed it (unzipped the packages and zipped back).....sorry If this confusing you....

Do not change any classes in your java directories.
If you need to use any of them, copy them somewhere else and edit them there if you need to.

[shana07]

Do not change any classes in your java directories.
If you need to use any of them, copy them somewhere else and edit them there if you need to.

Meaning to say that this is possible for me to do so isn't.
I need your advice regarding this please..
1. I have copied those two default java classes in my program under test
2. I renamed classes names as below:

java.math.BigIn teger >>> jonelo.sugar.ma th.MutableBigIn tegerMutant
java.math.Mutab leBigInteger >>> jonelo.sugar.ma th.BigIntMutant

3. And I have renamed all methods/variables/constructors with BigIntMutant
and MutableBigInteg erMutant

4. Is that possible for me to ask my program to refer to these two new classes when it calls gcd (I changed gcd method >>> gcdMutant).

case GCD:       out = b1.gcdMutant(b2).toString();
                            break;

When I compile my main program - these 3 errors occured, Please advise what should I do..thank you

Main.java:31: cannot find symbol
symbol : class BigIntMutant
location: package jonelo.sugar.ma th
import jonelo.sugar.ma th.BigIntMutant ;
^
Main.java:32: cannot find symbol
symbol : class MutableBigInteg erMutant
location: package jonelo.sugar.ma th
import jonelo.sugar.ma th.MutableBigIn tegerMutant;
^
Main.java:528: cannot find symbol
symbol : method gcdMutant(java. math.BigInteger )
location: class java.math.BigIn teger
case GCD: out = b1.gcdMutant(b2 ).toString();
^
3 errors

[r035198x]

Meaning to say that this is possible for me to do so isn't.
I need your advice regarding this please..
1. I have copied those two default java classes in my program under test
2. I renamed classes names as below:

java.math.BigIn teger >>> jonelo.sugar.ma th.MutableBigIn tegerMutant
java.math.Mutab leBigInteger >>> jonelo.sugar.ma th.BigIntMutant

3. And I have renamed all methods/variables/constructors with BigIntMutant
and MutableBigInteg erMutant

4. Is that possible for me to ask my program to refer to these two new classes when it calls gcd (I changed gcd method >>> gcdMutant).

case GCD: out = b1.gcdMutant(b2).toString();
break;

When I compile my main program - these 3 errors occured, Please advise what should I do..thank you

Main.java:31: cannot find symbol
symbol : class BigIntMutant
location: package jonelo.sugar.ma th
import jonelo.sugar.ma th.BigIntMutant ;
^
Main.java:32: cannot find symbol
symbol : class MutableBigInteg erMutant
location: package jonelo.sugar.ma th
import jonelo.sugar.ma th.MutableBigIn tegerMutant;
^
Main.java:528: cannot find symbol
symbol : method gcdMutant(java. math.BigInteger )
location: class java.math.BigIn teger
case GCD: out = b1.gcdMutant(b2 ).toString();
^
3 errors

First you will need to make sure that the classes you copied are not referencing other classes that you may not have copied.
Then you need to make sure that your import statements are correct e.g you cannot import a class that you are actually writting code for.

[shana07]

First you will need to make sure that the classes you copied are not referencing other classes that you may not have copied.
Then you need to make sure that your import statements are correct e.g you cannot import a class that you are actually writting code for.

good example. Help me take a look at this import of the Main class. Why when I compile the Main class comes that errors: can't find class from that import statement....

package jonelo.bigal;
import java.io.*;
import java.math.BigInteger;
import java.math.BigDecimal;
import jonelo.sugar.math.GeneralMath; // ** Check: This default class from this program
 
import jonelo.sugar.math.BigIntMutant; //** Check: That's why I put these altered class in here
import jonelo.sugar.math.MutableBigIntegerMutant; //** Check: same as this
 

[r035198x]

good example. Help me take a look at this import of the Main class. Why when I compile the Main class comes that errors: can't find class from that import statement....

package jonelo.bigal;
import java.io.*;
import java.math.BigInteger;
import java.math.BigDecimal;
import jonelo.sugar.math.GeneralMath; // ** Check: This default class from this program
 
import jonelo.sugar.math.BigIntMutant; //** Check: That's why I put these altered class in here
import jonelo.sugar.math.MutableBigIntegerMutant; //** Check: same as this
 

Did you set up the directory structure correctly?