CODEWITHSUNDEEP
javapythonstringequals
user12245018
user12245018

Reputation:

What is the difference between python and java == operator

Can somebody explain to me why Python is able to print the following statement bellow while Java doesn't. I know it's something to do with == in Java and equals() but I don't really understand the difference.

Python code

str1 = "Pro"
str2 = str1 + ""

if str1 == str2:
   print("the strings are equal")```

Java Code

public class StringEq {
    public static void main(String[] args) {
        String str1 = "Pro";
        String str2 = str1 + "";

       if (str1 == str2) {
            System.out.println("The strings are equal");
        }
     }
 }

Upvotes: 3

Views: 1393

Answers (3)

Ryuzaki L
Ryuzaki L

Reputation: 40078

In python == is used to compare the content of the objects by overriding the operator.eq(a, b) method, str class has overridden this in order to compare the content of objects 

These are the so-called “rich comparison” methods. The correspondence 
between operator symbols and method names is as follows: x<y calls 
x.__lt__(y), x<=y calls x.__le__(y), x==y calls x.__eq__(y), x!=y calls 
x.__ne__(y), x>y calls x.__gt__(y), and x>=y calls x.__ge__(y).

But in java == operator is used compare the reference of objects here

Using the “==” operator for comparing text values is one of the most common mistakes Java beginners make. This is incorrect because “==” only checks the referential equality of two Strings, meaning if they reference the same object or not.

so in java to compare the content of object you have to use equals which is overridden in String class.

if (str1.equals(str2))

so java == operator is equal to is operator in python which compare both references are pointed to same object or not

Upvotes: 1

Carcigenicate
Carcigenicate

Reputation: 45806

Python's str class uses value-equality for its __eq__ method. In Python, classes can override __eq__ to define how == behaves.

Contrast that with Java where == always does reference-equality. In Java, == will only return true if both objects are literally the same object; regardless of their content. Java's == is more comparable to Python's is operator.

A better comparison, as noted in the comments, would be to compare these:

"a".equals("a")  // Java

"a" == "a"  # Python

Java's String class has its equals do a value equality instead of of reference equality.

Upvotes: 3

Cat Bisque
Cat Bisque

Reputation: 206

It explains it well here:

And here is a quote from that site: "We can use == operators for reference comparison (address comparison) and .equals() method for content comparison. In simple words, == checks if both objects point to the same memory location whereas .equals() evaluates to the comparison of values in the objects."

Upvotes: 1

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