Casting and Range of Variables

Learning Objectives

1. Develop code to cast primitive values to different primitive types in arithmetic expressions and determine the value that is produced as a result.
   • The casting operators (int) and (double) can be used to convert from a double value to an int value (or vice versa).
   • Casting a double value to an int value causes the digits to the right of the decimal point to be truncated.
   • Some code causes int values to be automatically cast (widened) to double values.
   • Values of type double can be rounded to the nearest integer by (int) (x + 0.5) for non-negative numbers or (int)(x - 0.5) for negative numbers.
2. Describe conditions when an integer expression evaluates to a value out of range.
   • The constant Integer.MAX_VALUE holds the value of the largest possible int value. The constant Integer.MIN_VALUE holds the value of the smallest possible int value.
   • Integer values in Java are represented by values of type int, which are stored using a finite amount (4 bytes) of memory. Therefore, an int value must be in the range from Integer.MIN_VALUE to Integer.MAX_VALUE inclusive.
   • If an expression would evaluate to an int value outside of the allowed range, an integer overflow occurs. The result is an int value in the allowed range but not necessarily the value expected.
3. Describe conditions that limit accuracy of expressions.
   • Computers allot a specified amount of memory to store data based on the data type. If an expression would evaluate to a double that is more precise than can be stored in the allotted amount of memory, a round-off error occurs. The result will be rounded to the representable value. To avoid rounding errors that naturally occur, use int values.