CODEWITHSUNDEEP
javacompareequals
Paolo Forgia
Paolo Forgia

Reputation: 6748

Why does Long equals return false when are the same value?

Running the following code I expect true as result, but the output I get is false.

Long value = new Long(0);
System.out.println(value.equals(0));

Why does the equals comparison of Long return false?

Upvotes: 1

Views: 5529

Answers (3)

Niton
Niton

Reputation: 306

You compared an Long with an int!
the .equals method also is checking the type of the Variable.
Here is a code to campare an int with an long: 

int i = 0;
long l = 0L;

//v1
System.out.println(i == l);
//v2
Long li = new Long(i);
Long ll = new Long(l);
System.out.println(li.eqauls(ll));
//v3
System.out.println(((long)i) == l);

Upvotes: 0

ΦXocę 웃 Пepeúpa ツ
ΦXocę 웃 Пepeúpa ツ

Reputation: 48258

looking inside in the implemented compare method you will find the critical criteria:

if (obj instanceof Long) 



public boolean equals(Object obj) {
    if (obj instanceof Long) {
        return value == ((Long)obj).longValue();
    }
    return false;
}

so passing any other numeric type will return false, even if the hold the same value...

Integer i = 0;

and 

Long l = 0L;

are not the same in that context.

Upvotes: 3

Paolo Forgia
Paolo Forgia

Reputation: 6748

Long.equals return true only if the argument is also a Long.

The javadoc says:

Compares this object to the specified object. The result is true if and only if the argument is not null and is a Long object that contains the same long value as this object.

In fact the following code gets true as output.

Long value = new Long(0);
System.out.println(value.equals(new Long(0)));
System.out.println(value.equals((long) 0));
System.out.println(value.equals(0L);

Upvotes: 5

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