CODEWITHSUNDEEP
java
Rahul_891
Rahul_891

Reputation: 39

trying to find range of long data type in java

trying to verify range of long in java.. why is this program not working? it gives infinite loop (probably). i'm not getting output at the command line and the cursor keeps blinking.

class range
{
public static void main(String [] args)
{
         long i;
     for(i=0;;i++)
    {
         long c= (long)(i+1);
         if(i>c)    //upper_limit+1=lower_limit
            break;  // hence, at i=upper_limit c(=i+1) < i

    }
    System.out.println("upper ="+i);
    for(i=-1;;i--)
    {
        long c=(long)(i-1);         
        if(i<c)             //lowerlimit-1=upperlimit
            break;          //hence at i=lowerlimit c(=i-1)>i
    }
    System.out.println("lower ="+i);
}
}

Upvotes: 1

Views: 353

Answers (4)

Andy
Andy

Reputation: 3743

There is no reason to start at 0 or -1.

If you want to verify MIN/Max values, try it like this:

class range
{
public static void main(String [] args)
{
         long i;
     for(i=Long.MAX_VALUE;;i++)
    {
         long c= (long)(i+1);
         if(i>c)    //upper_limit+1=lower_limit
            break;  // hence, at i=upper_limit c(=i+1) < i

    }
    System.out.println("upper ="+i);
    for(i=Long.MIN_VALUE;;i--)
    {
        long c=(long)(i-1);         
        if(i<c)             //lowerlimit-1=upperlimit
            break;          //hence at i=lowerlimit c(=i-1)>i
    }
    System.out.println("lower ="+i);
}
}

Upvotes: 0

kostya
kostya

Reputation: 9559

You can use Long.MAX_VALUE and Long.MIN_VALUE

It will take lots of time to enumerate all 2^64 possible long values

Upvotes: 0

Ivaylo Strandjev
Ivaylo Strandjev

Reputation: 70989

Why do you think your program is not correct? It simply will take a long while - until long overflows(about 2^63 iterations). I suggest that you use Long.MIN_VALUE and Long.MIN_VALUE or if you want to avoid this solution use binary search for when overflow happens.

Also you may consider using the same program for short to verify it is correct, simply very time consuming.

Upvotes: 1

Jon Skeet
Jon Skeet

Reputation: 1502246

Your program will work eventually - but it's got to perform 263 iterations (in each direction) first. That's going to take a very long time. Long.MAX_VALUE and Long.MIN_VALUE are rather simpler ways of finding this out. Or just look at JLS 4.2.1:

The values of the integral types are integers in the following ranges:

  • ...

  • For long, from -9223372036854775808 to 9223372036854775807, inclusive

If you want to see your program finding the right values, just start it closer to the final result:

for(i=Long.MAX_VALUE - 10;;i++)
...
for(i=Long.MIN_VALUE + 10;;i--)

That quickly ends with output of:

upper =9223372036854775807
lower =-9223372036854775808

Upvotes: 7

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