While comparing two values in Java, how do you test if both, the type and the value, are equivalent?
I know in JavaScript === can be used to accomplish this, so I tried that in Java, but it didn’t work.
I know this is a simple question, but I tried looking it up and I couldn’t find out what it was.
TL;DR
In Java there is not such a comparison operator: ===, but == or equals
A longer explanation
In weakly typed languages such as JavaScript you can use the strict comparison operator (===) because the language allows comparison between variables which have different types.
For example, in JavaScript, you won't get a compile error if you do this:
var x = 10;
var y = 'foo';
console.log(x == y); // false
And it is useful, when you want to compare variables which may hold values that are "equals" but may be of different types.
For example
var x = 10;
var y = '10';
console.log(x == y) // true
console.log(x === y) // false
In strongly typed languages such as Java, you don't need to use a strict comparison operator because the language already "handles" the type comparison.
For example:
int x = 10;
String y = "10";
System.out.println("10" == y); // true
System.out.println(x == y); // compile error : Incompatible operand types int and String
So, basically, in Java, there is no need for checking for strictness using === (a syntax error is reported).
In the first place, the compiler will complain when you compare values of different types using the == operator and conversion cannot be performed.
In the previous example of Java code, if you want to make a comparison between x and y you could use equals:
int x = 10;
String y = "10";
System.out.println(y.equals(x)); // compile warning: Unlikely argument type for equals(): int seems to be unrelated to String
As a side note, notice the equals method cannot be called on primitive types.
Some useful readings are: