Java know how much (11) data type conversions

Conversions of data types are divided into automatic conversions and casts. Automatic conversion is a program in the execution of the "quietly" conversion, do not require the user to declare in advance, generally from a low number of bits of the type to a high number of bits conversion; Coercion type conversions must be declared in code and the order of conversion is not restricted.

Automatic data type conversions

Automatic conversions are converted in order from low to high. The priority relationships between different types of data are as follows:
Low---------------------------------------------> High
byte,short,char-> int, long, float---double

Operations, different types of data are converted to the same type first, then the operation, the conversion rules are as follows:

operand 1 Type	operand 2 Type	the converted type
Byte, short, Char	Int	Int
Byte, short, char, int	Long	Long
Byte, short, char, int, long	Float	Float
Byte, short, char, int, long, float	Double	Double

Forcing data type conversions

The format of the cast is to add "()" before the data that needs to be transformed, and then add the data type that needs to be converted in parentheses. Some data after transformation operation, the accuracy will be lost, and some will be more accurate, the following example can illustrate this problem.

1  Public classDemo {2  Public Static voidMain (string[] args) {3  　　 intx;4  　　　　 Doubley;5x = (int) 34.56 + (int) 11.2;//Loss of Precision6y = (Double) x + (Double) 10 + 1;//Improved accuracy7System.out.println ("x=" +x);8System.out.println ("y=" +y);9  　　 }Ten}

Operation Result:

x=45y=56.0

Carefully analyze the above program segment: Since there is a forced type conversion of int before 34.56, 34.56 becomes 34. The same 11.2 becomes 11, so the result of X is 45. There is a cast of type double before x, so the value of x becomes 45.0, and the front of 10 is also coerced to a double type, so it becomes 10.0, so the value of the last Y becomes 56.

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