2 0 FUNDAMENTALS OF JAVA PROGRAMMING LANGUAGE 2

2. 0 FUNDAMENTALS OF JAVA PROGRAMMING LANGUAGE 2. 3 Use operator to modify values. 1

FP 301 OBJECT ORIENTED PROGRAMMING Learning Outcome Subtopic 2. 3 1 • Modify variable values using operator: . 2 • Apply the rules of precedence for an expression in modifying variables values 3 • Explain type casting and promotion in Java programs 4 • Implement type casting and promotion to change the data types 2

FP 301 OBJECT ORIENTED PROGRAMMING STANDARD MATHEMATICALS OPERATORS Purpose Addition Subtraction Multiplication Division Operator Example + sum = num 1 + num 2; If num 1 is 10 and num 2 is 2, sum is 12. - diff = num 1 – num 2; If num 1 is 10 and num 2 is 2, diff is 8. * / Comments prod = num 1 * num 2; If num 1 is 10 and num 2 is 2, prod is 20. quot = num 1 / num 2; If num 1 is 31 and num 2 is 6, quot is 5. Division returns an integer value (with no remainder). 3

FP 301 OBJECT ORIENTED PROGRAMMING Cont. . Purpose Operator Remainder % Example mod = num 1 % num 2; If num 1 is 31 and num 2 is 6, mod is 1. Comments Remainder finds the remainder of the first number divided by the second number. Remainder always gives an answer with the same sign as the first operand. 4

FP 301 OBJECT ORIENTED PROGRAMMING INCREMENT AND DECREMENT OPERATORS ( ++ and -- ) i) The long way : age = age + 1; ii) The short way : Operator ++ Purpose Example Pre-increment (++variable) int i = 6; int j = ++i; i is 7, j is 7 Post-increment (variable++) int i = 6; int j = i++; i is 7, j is 6 Notes The value of i is assigned to j before i is incremented. Therefore, j is assigned 6. 5

FP 301 OBJECT ORIENTED PROGRAMMING Cont. . Operator -- Purpose Example Pre-decrement (--variable int i = 6; int j = --i; i is 5, j is 5 Post decrement (variable--) int i = 6; int j = i--; i is 5, j is 6 Notes The value i is assigned to j before i is decremented. Therefore, j is assigned 6. 6

FP 301 OBJECT ORIENTED PROGRAMMING LOGICAL OPERATORS • The boolean operators are: ! : NOT & : AND | : OR ^ : XOR • The short-circuit boolean operators are: && : AND || : OR • You can use these operators as follows: My. Date d = reservation. get. Departure. Date(); if ( (d != null) && (d. day > 31) { // do something with d } 7

FP 301 OBJECT ORIENTED PROGRAMMING BITWISE LOGICAL OPERATORS • The integer bitwise operators are: ~ : Complement (vice versa) & : AND (only true will become true) ^ : XOR (x+y) % 2 | : OR (only false will become false) • Byte-sized examples include: ~ 0 1 1 0 ^ 0 0 1 1 1 0 0 1 1 0 1 0 0 1 1 0 0 0 1 0 & | 0 0 1 1 0 1 0 0 1 1 0 0 1 1 0 1 1 1 1 8

FP 301 OBJECT ORIENTED PROGRAMMING RIGHT-SHIFT OPERATORS • Arithmetic or signed right shift (>>) operator: • Examples are: 128 >> 1 returns 128/21 = 64 256 >> 4 returns 256/24 = 16 -256 >> 4 returns -256/24 = -16 • The sign bit is copied during the shift. • Logical or unsigned right-shift (>>>) operator: • This operator is used for bit patterns. • The sign bit is not copied during the shift. 9

FP 301 OBJECT ORIENTED PROGRAMMING LEFT-SHIFT OPERATORS Left-shift (<<) operator works as follows: 128 << 1 returns 128 * 21 = 256 16 << 2 returns 16 * 22 = 64 10

FP 301 OBJECT ORIENTED PROGRAMMING SHIFT OPERATOR EXAMPLES 11

FP 301 OBJECT ORIENTED PROGRAMMING STRING CONCATENATION WITH ‘+’ • The + operator works as follows: • Performs String concatenation • Produces a new String: String salutation = "Dr. "; String name = "Pete" + "Seymour"; String title = salutation + " " + name; • One argument must be a String object. • Non-strings are converted to String objects automatically. 12

FP 301 OBJECT ORIENTED PROGRAMMING APPLY THE RULES OF PRECEDENCE FOR AN EXPRESSION IN MODIFYING VARIABLES VALUES Example : Applying the operator precedence and associativity rule, the expression 3 + 4 * 4 > 5 * (4 + 3) - 1 is evaluated as follows: 13

FP 301 OBJECT ORIENTED PROGRAMMING TYPE CASTING AND PROMOTIONS IN JAVA PROGRAMS Type Casting refers to changing an entity of one datatype into another. • Example of potential issue: int num 1 = 53; // 32 bits of memory to hold the value int num 2 = 47; // 32 bits of memory to hold the value byte num 3; // 8 bits of memory reserved num 3 = (num 1 + num 2); // causes compiler error • Example of potential solution: int num 1 = 53; int num 2 = 47; long num 3; num 3 = (num 1 + num 2); 14

FP 301 OBJECT ORIENTED PROGRAMMING Cont. . • Variables are promoted automatically to a longer form (such as int to long). • Expression is assignment-compatible if the variable type is at least as large (the same number of bits) as the expression type. long bigval = 6; // 6 is an int type, OK int smallval = 99 L; // 99 L is a long, illegal double z = 12. 414 F; // 12. 414 F is float, OK float z 1 = 12. 414; // 12. 414 is double, illegal 15