CODEWITHSUNDEEP
javaintlong-integer
Goozo
Goozo

Reputation: 956

Simple Java integer and long arithmetics

Simple code no problem

long x =  Integer.MAX_VALUE;
System.out.println(x * 2 + "...." + Long.MAX_VALUE);

= 4294967294....9223372036854775807

but what is happening here? why -2

System.out.println(2 * Integer.MAX_VALUE + "...." + Long.MAX_VALUE);
=   -2....9223372036854775807

and why elements is 149998, doesn't the compiler converts these to long? 

    long elements = 2 * Integer.MAX_VALUE + 150000;
System.out.println(elements + "...." + Long.MAX_VALUE);
149998....9223372036854775807

-thanks

Upvotes: 0

Views: 223

Answers (4)

ChriskOlson
ChriskOlson

Reputation: 513

I don't have enough rep to comment yet :(.

The Oracle Java Tutorials confirmed that it will convert the data to the primitive type long. Since you're adding an int and a long, the compiler will add the data before it converts it to a long. If you really want it to be a long the entire time, you'd have to type cast.

EX;

 // (long) is typcasted
long elements = 2 * (long) Integer.MAX_VALUE + 150000;

//prints elements as a long t + "" + max value
System.out.println(elements + "...." + Long.MAX_VALUE);

Type is casting preformed by adding the wanted primitive type in front of the current data type.

Upvotes: 0

Bruce Lowe
Bruce Lowe

Reputation: 6213

and why elements is 149998, doesn't the compiler converts these to long?

It does, but only after the arithmetic. So you've got int*int + int, which is an int. It will then cast it to a long. However, at this point you've got an integer overflow (i.e. it went beyond the bounds of an integer)

you need to convert the numbers of the right to a long first 

long elements = 2L * Integer.MAX_VALUE + 150000;

or

long elements = 2 * (long)Integer.MAX_VALUE + 150000;

B

Upvotes: 3

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35587

Integer.MAX_VALUE =2147483647=01111111 11111111 11111111 11111111

And 

2*Integer.MAX_VALUE=4294967294=2*(01111111 11111111 11111111 11111111)  
                              =this will result a 33-bit value

But in Java int can represent maximum of 32bit.

Upvotes: 1

Prince John Wesley
Prince John Wesley

Reputation: 63708

Promote variables from integer to long. 

long elements = 2 * Integer.MAX_VALUE + 150000;

should be

long elements = 2L * Integer.MAX_VALUE + 150000;

The evaluation of original statement,

long elements = 2 * Integer.MAX_VALUE + 150000;

is equivalent to 

long elements = (long)(2 * Integer.MAX_VALUE + 150000);

Upvotes: 6

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