Comparing an int and Integer in Java

Question

Consider the following snippet:

Integer Foo = 2;
int foo = 1;
boolean b = Foo < foo;

is < done using int or Integer? What about ==?

Duplicate: stackoverflow.com/questions/3352791/… or stackoverflow.com/q/7672317/1743880. Even better stackoverflow.com/q/9150446/1743880. Also stackoverflow.com/questions/31572567/integer-vs-int-comparison — Tunaki
– Tunaki, Commented Mar 9, 2016 at 22:30

Bathsheba · Accepted Answer · 2016-03-09 22:27:51Z

4

For all the relational operators (including therefore < and ==), if one type is the boxed analogue of the other, then the boxed type is converted to the unboxed form.

So your code is equivalent to Foo.intValue() < foo;. This is deeper than you might think: your Foo < foo will throw a NullPointerException if Foo is null.

answered Mar 9, 2016 at 22:27

Bathsheba

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Sergey Kalinichenko · Accepted Answer · 2016-03-09 22:32:00Z

3

According to JLS, 15.20.1

The type of each of the operands of a numerical comparison operator must be a type that is convertible (§5.1.8) to a primitive numeric type, or a compile-time error occurs. Binary numeric promotion is performed on the operands (§5.6.2).

Further, 5.6.2 states that

If any operand is of a reference type, it is subjected to unboxing conversion

This explains what is happening in your program: the Integer object is unboxed before the comparison is performed.

answered Mar 9, 2016 at 22:32

Sergey Kalinichenko

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Geralt_Encore · Accepted Answer · 2016-03-09 22:29:28Z

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They will be done using int due to Autoboxing and Unboxing.

answered Mar 9, 2016 at 22:29

Geralt_Encore

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1 Comment

Monroy Over a year ago

This is also a useful resource stackoverflow.com/questions/27647407/…

meet thakkar · Accepted Answer · 2016-03-09 22:31:08Z

0

The Wrapper types for primitive types in java does automatic "type casting" ( or autoboxing / unboxing) from Object to compatible primitive type. so Integer will be converted to int before passing it to comparison operators or arithmetic operators like < , > , == , = , + and - etc.

answered Mar 9, 2016 at 22:31

meet thakkar

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