Sad reality about Wrapper Classes in Java
Consider the snippet.
Integer firstInteger = 1000; // autoboxing
Integer secondInteger = 1000; //autoboxing
if (firstInteger != secondInteger) {
System.out.println("Different objects!");
}
if(firstInteger.equals(secondInteger)) {
System.out.println("Meaningfully equivalent!");
}
Output:
Different objects! Meaningfully equivalent!
How about this one.
Integer firstInteger = 100; // autoboxing
Integer secondInteger = 100; //autoboxing
if (firstInteger == secondInteger) {
System.out.println("Equal objects!");
}
if(firstInteger.equals(secondInteger)) {
System.out.println("Meaningfully equivalent!");
}
And the output?
Equal objects! Meaningfully equivalent!
And the explanation?
Two instances of the wrapper objects will always be == when their primitive values are the same.
- Boolean
- Byte
- Character from \u0000 to \u007F (0 to 127)
- Short from -128 to 127
- Integer from -128 to 127
Tsk.
