Java6: Adding primitive member vars. to TreeSet<Generics>

[andrew222]

I have a question to ask about Java 6. Today I tried to declare a TreeSet with a Generic type as Double as seen below..I was putting primitive double values which are member fields of a class I designed into the TreeSet.


TreeSet<Double> ts = new TreeSet<Double>();

Then after doing so, Eclipse told me that I can't do such an operation in Java 6 and had to change the compliance to work with Java 5.0.

What I can't figure out is why? I made a prototype that puts straight primitive double values into a TreeSet with no error. Now my deductive reasoning tells me that it has a problem using a primitive field of my class.

Does anyoneone know what specific changes were made to the API to make this happen?


Here is the whole program below...



import java.util.*;

class SP
{
String name;
double percentageChange;

SP()
{this.name=null;this.percentageChange=0.0;}


SP (String i_name, double i_percentageChange)
{
this.name = i_name;
this.percentageChange = i_percentageChange;
}
}


public class TreeSetDemo
{


public static void main(String [] args)
{
System.out.println("S&P's Best and Worst Performing Stocks of 2008");
System.out.println("http://seekingalpha.com/article/112981-s-p-s-best-and-worst-of-2008\n\n");

SP lb = new SP("Lehman Brothers", -99.96);
SP wm = new SP("Washington Mutual", -99.84);
SP wr = new SP("Wrigley", 36.58);
SP fd = new SP("Family Dollar", 35.57);
SP fm = new SP("Fannie Mae", -98.10);
SP frm = new SP("Freddie Mac", -97.86);
SP aig = new SP("AIG", -97.31);
SP cc = new SP("Circuit City", -96.90);
SP ab= new SP("Anheuser-Busch", 31.03);
SP ust = new SP("UST", 26.61);
SP am = new SP("Amgen", 24.35);
SP bph = new SP("Barr Pharma", 23.92);
SP ggp = new SP("General Growth Properties", -96.87);
SP ew = new SP("EW Scripps", -95.09);
SP abk = new SP("Ambac Financial", -94.96);
SP bs = new SP("Bear Stearns", -89.43);
SP nc = new SP("National City", -89.00);
SP gf = new SP("Genworth Financial", -88.88);
SP dd = new SP("Developers Diversified",-87.26);

SP [] spArr = {lb, wm, wr, fd,fm,frm, aig,cc,ab,ust,am,bph,ggp,ew,abk,bs,nc,gf,dd};

/*I have Java 6 installed and had to change worspace compliance to Java 5.0 in order to
make the declaration below work*/
TreeSet<Double> ts = new TreeSet<Double>();



System.out.println("Name" + ": " + "Percentage Change" );
System.out.println("-------------------------");
for(int i =0; i < spArr.length; i++)
{
ts.add(spArr[i].percentageChange);
System.out.println(spArr[i].name + ": " + spArr[i].percentageChange + '\n');

}
System.out.println("\nS&P 2008 stocks percentage change values above sorted from least to greatest ");
System.out.println("There are "+ts.size() + " elements in this TreSet");
System.out.println("The TreeSet dectects the lowest element as: " + ts.first());
System.out.println(ts + "\n\n");
System.out.println("Between the range: 20.0--30.0");
System.out.println(ts.subSet(20.00,30.00));
System.out.println("\nBetween the range: 30.0--40.0");
System.out.println(ts.subSet(30.00,40.00));
System.out.println("\nBetween the range: -100.0--(-90.0)");
System.out.println(ts.subSet(-100.00,-90.00));
System.out.println("\nBetween the range: -90.0--(-80.0)");
System.out.println(ts.subSet(-90.00,-80.00));



}

}



Ok, here is the prototype I talked about


import java.util.*;


public class demo {

public static void main(String [] args)
{
double [] d = {11.11,22.22,33.33};
TreeSet<Double> ts = new TreeSet<Double>();

ts.add(d[0]);

}
}

[CptPicard]

Could you give the exact error you're getting? Can you isolate the problem into a more concise demonstrative case?

You should be really cautious about putting floating-point numbers into a set like that, by the way -- their equality is tricky, and especially after arithmetic operations two of them are rarely equal in practice although mathematically they would be.

[Reiger]

You need to box it first, like so:
(modified your prototype)


import java.util.*;


public class demo {

public static void main(String [] args)
{
double [] d = {11.11,22.22,33.33};
TreeSet<Double> ts = new TreeSet<Double>();

ts.add(new Double(d[0]));

}
}

[muntasir_120]

The (shorter) code compiles without any errors or warnings on compiling in jdk1.6 with javac. The problem must be with eclipse.

[andrew222]

CtpPicard: I received the error message as a "red box error" from Eclipse which plainly told me as an itelli-sense option "change workspace compliance to Java 5.0 in order to make the declaration work". I searched the API to find any changes and then came here to see if anyone else has experienced this.

Actually, I started a new project and pasted the exact code into a new class to reproduce the error from Eclipse and did not get one. We all know how Eclipse complains about things like uninitialized variables etc. when typing in code Anyways, I feel bad that I can't reproduce the actual error for you.

I do agree that it is bad practice to compare floating point values (can strictfp help this?) but this is just a prototype that I am doing for training in Consultancy.



Reiger: I agree that the new "Double" in the add statement is needed as well.

Thank you and have a pleasant weekend,

Andrew

[CptPicard]

You might want to try a clean/rebuild in the old project, or something... it sounds weird.

As regards the floating point... BigDecimal probably would be the way to go in this case.