1. Primitive Types CSE 115 Spring 2006 April 3 & 7 2006

2. Type  A set of values and the operations we can do with those values.

3. Object Types vs. Primitive Types  We have been using object types all semester.  Primitive types are another type built into Java.  The distinction between these two types has been significantly blurred by Java 5.

4. Primitive Types  Primitive Types ≠ Objects  The way we create them is different.  Primitive types have a value.  Objects have instance variables.  Primitive types have operations we can perform on them.  Objects have methods we can call on them.

5. Types of Primitives  Numbers  Booleans  Characters

6. Numbers  Whole Numbers  byte – 1 byte (-128 to 127)  short – 2 bytes  int – 4 bytes (-2147483648 to 2147483647)  long – 8 bytes

7. Operations on Numbers (Unary) +  Promotes a byte, short or char to an int -  Unary negation ++  Increment --  Decrement

8. Operations on Numbers (Binary) +  Addition -  Subtraction *  Multiplication /  Division %  Modulus

9. Important Note  In Java, operations on integers are closed. This means that an operation performed on an integer returns an integer, or likewise, an operation performed on two integers returns an integer.

10. More Numbers  Real/floating point numbers  float  double  Operations: Same as for whole numbers

11. Important note  Operations on two real numbers return a real number.  Operations on a real number and a whole number return a real number.

12. How to get the “real” answer to the division of two integers?  Typecasting – we can force Java to believe that we are doing floating point arithmetic. int a = 1; int b = 2; double realAnswer = (double)1/2;

13. Booleans  Two-valued algebra system  True  False  The boolean values in Java are true and false (not 0 and 1).

14. Operations that return boolean values <  Less than >  Greater than <=  Less than or equal to >=  Greater than or equal to ==  Equals !=  Not equals

15. Operations performed on booleans (Unary)  Negation (not)  Symbol: !  Meaning: p!p truefalse falsetrue

16. Operations performed on booleans (Binary)  Conjunction (and)  Symbol: &&  Meaning:  Disjunction (or)  Symbol: ||  Meaning: pq p && q truetruetrue truefalsefalse falsetruefalse falsefalsefalsepq p || q truetruetrue truefalsetrue falsetruetrue falsefalsefalse

17. Short circuit boolean evaluation  Java supports short circuit boolean evaluation.  This means that if there is a false in a conjunction or a true in a disjunction, Java stops evaluating the expression and produces the result.

18. Characters  Single letter, digit, or symbol  Character literals are surrounded by ‘’ in code: char aCharacter = ‘x’;  Character class has methods of interest when working with characters.

19. String  Not a primitive type  Sequence of characters  String literals are surrounded by “” in code String greeting = “Hi there!”;

20. String concatenation  Can combine strings together using the + operator. String one = “light”; String two = “house; String result = one + two;  result now has the value “lighthouse”

21. String concatenation  You can also combine a string with a primitive type. int a = 5; int b = 6; int result = a * b; String output = “The result of multiplying 5 and 6 is: ” + result;

22. String Class  There are many useful methods for String available in the String class.