Java Integer.MAX_VALUE and Integer.MIN_VALUE

Question

Following code

BigInteger number=new BigInteger("2154789654785210095153123254756845");
boolean b=number.longValue()>Long.MIN_VALUE;
boolean c=number.longValue()<Long.MAX_VALUE;
boolean d=number.longValue()>=Integer.MIN_VALUE;
boolean e=number.longValue()<=Integer.MAX_VALUE;
System.out.println(""+b);
System.out.println(""+c);
System.out.println(""+d);
System.out.println(""+e);

generates output

true
true
false
true

Keeping in mind that after achieving MAX_VALUE in Integer,value goes back to MIN_VALUE and loops again, if a value is <=Integer.MAX_VALUE , then it must be >=Integer.MIN_VALUE , then why does boolean variable d returns false ?

Answer 1

This can be explained once we understand what longValue() is returning.

Converts this BigInteger to a long. This conversion is analogous to a narrowing primitive conversion from long to int as defined in section 5.1.3 of The Java™ Language Specification: if this BigInteger is too big to fit in a long, only the low-order 64 bits are returned. Note that this conversion can lose information about the overall magnitude of the BigInteger value as well as return a result with the opposite sign.

Printing the value of this variable yields -4694333933485660691 , a value that is certainly a legal long value but is far less than Integer.MIN_VALUE (which is implicitly converted to a long here), so false is correct for the d printout.

Both the b and c outputs are true because the value -4694333933485660691 is greater than Long.MIN_VALUE , and because the value -4694333933485660691 is less than Long.MAX_VALUE . The only values that would print false for b and c are those BigInteger s that would convert to Long.MIN_VALUE AND Long.MAX_VALUE themselves, respectively, when longValue() is called.

Answer 2

It can be easily understood by printing values as below

number.longValue()[-4694333933485660691]>Long.MIN_VALUE[-9223372036854775808  =  true
number.longValue()[-4694333933485660691]<Long.MAX_VALUE[9223372036854775807  =  true
number.longValue()[-4694333933485660691]>=Integer.MIN_VALUE[-9223372036854775808  =  false
number.longValue()[-4694333933485660691]<=Integer.MAX_VALUE[9223372036854775807  =  true

Hope this helps

Answer 3

从Java 1.8开始，您可以使用BigInteger.longValueExact() ，如果BigInteger值无法精确表示为long值，则会抛出ArithmeticException 。