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javavariablesfloating-point
m4tx
m4tx

Reputation: 4511

What is the Difference between float "1" and float "1f" in Java?

Is there any difference - in Java - between defining float variables like, e.g., this: 1 and this: 1f? Is the JVM doing any casts at run-time when I write 1, or something that could slow down my app?

Regards

Upvotes: 2

Views: 28106

Answers (6)

GuilhE
GuilhE

Reputation: 11861

float a = 1;
float b = 1f;

It's the same, but if you do something like:

int a = 1f

Will throw "Type mismatch: cannot convert from float to int"

int b = 1d or 1.0

Will throw "Type mismatch: cannot convert from double to int"

float c = 1d or  1.0

Will throw "Type mismatch: cannot convert from double to float"

Note that:

double a = 2.0;
double b = 2d;
double c = 2.0f;
if (a == b) {
    if (c == a) {
        if (c == b) {
            return 1;
        }
    }
}

Will return 1;


Regards.

Upvotes: 4

manurajhada
manurajhada

Reputation: 5380

Yes, there is a big difference between 1 and 1f. As you can't declare a variable without giving its type in java, Its clear 1 is an int and 1f denotes float at compile time itself. This is nothing related to run time or slow down your app.

Upvotes: 1

vbezhenar
vbezhenar

Reputation: 12326

Java code

    float f1 = 1;
    float f2 = 1f;

compiles to following bytecode:

     0: fconst_1      
     1: fstore_1      
     2: fconst_1      
     3: fstore_2

As you can see, there's no difference at run-time.

Upvotes: 4

Crazenezz
Crazenezz

Reputation: 3456

If the case like this the JVM will pass it.

public class Test {

    public static void main(String[] args) {
        float f = 1;
        System.out.println(f);
    }
}

But it will occur exception if you do something like this:

public class Test {

    public static void main(String[] args) {
        float f = 1.5;
    }
}

Exception:

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - possible loss of precision
  required: float
  found:    double
    at package.Test.main(Test.java:17)

What we can analyze for this two example is, for the first example it automatically converted to float, but for the second example if you add some decimal point without the f or F suffix than it will automatically converted to double.

Upvotes: 2

Andreas Johansson
Andreas Johansson

Reputation: 1145

Basically 1 will default to an int. If you write 1f it will be considered a float. If you write 1.0 (no f) it will default to a double.

A floating-point literal is of type float if it is suffixed with an ASCII letter F or f; otherwise its type is double and it can optionally be suffixed with an ASCII letter D or d.

For more info about java data types.

Upvotes: 4

Jigar Joshi
Jigar Joshi

Reputation: 240900

1 is implicitly considered as int literal where 1f is considered as float literal

See

Upvotes: 6

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