In Java, when you type a decimal number as 3.6, its interpreted as a double. double is a 64-bit precision IEEE 754 floating point, while floatis a 32-bit precision IEEE 754 floating point. As a float is less precise than a double, the conversion cannot be performed implicitly.
If you want to create a float, you should end your number with f (i.e.: 3.6f).
For more explanation, see the primitive data types definition of the Java tutorial.
Make it
float b= 3.6f;
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
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