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Questions and Answers
What is the order of evaluation for unary operators of the same level?
What is the purpose of using variables in the Receipt program?
What is the result of the expression z - (a + b / 2) + w * -y given the values z = 8, a = 3, b = 9, w = 2, and y = -5?
What is the purpose of type casting in programming?
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What is the benefit of using variables in the Receipt program for the subtotal, tax, and tip?
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What is the order of operations for the expression z - (a + b / 2) + w * -y?
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What is the purpose of the subtotal variable in the Receipt program?
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What is the result of the expression 38 + 40 + 30?
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What is the purpose of the tax and tip variables in the Receipt program?
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What is the final result of the Receipt program?
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Study Notes
Data Types
-
byte: 8 bytes -
double: 8 bytes, range of about ±10^308, 15 significant decimal digits -
float: 4 bytes, range of about ±10^38, 7 significant decimal digits -
char: 2 bytes, represents code units in Unicode encoding scheme -
boolean: 1 bit, has two truth values:falseandtrue
Expressions
- An expression is a value or operation that computes a value
- Examples of expressions:
1 + 4 * 5,(7 + 2) * 6 / 3,42 - Simplest expression is a literal value, such as
42or28.9 - Complex expressions can use operators, operands, and parentheses
Arithmetic Operators
-
+: addition -
-: subtraction (or negation) -
*: multiplication -
/: division -
%: modulus (remainder)
Evaluation
- The process of obtaining the value of an expression
- Expressions are evaluated as a program runs
- Examples:
1 + 1evaluates to2,System.out.println(3 * 4)prints12
Integer Division
- When dividing integers, the quotient is also an integer
- Example:
4 / 2is2, not2.0
String Concatenation
- Using
+between a string and another value to make a longer string - Examples:
"hello" + 42is"hello42","abc" + 1 + 2is"abc12"
Variables
- Declaration syntax:
type name; - Initialization syntax:
type name = value; - Example:
int x;,double myGPA = 3.95; - Variables can be used in expressions:
int x = 3; System.out.println("x is " + x); - Variables can be assigned a value more than once:
x = 4 + 7;
Assignment and Algebra
- Assignment uses
=, but it is not an algebraic equation -
=means "store the value at right in variable at left" - The right side expression is evaluated first, and then its result is stored in the variable at left
Compiler Errors
- A variable can't be used until it is assigned a value
- A variable can't be declared twice
- Example:
int x;,int x;is an error
Printing a Variable's Value
- Use
+to print a string and a variable's value on one line - Example:
double grade = (95.1 + 71.9 + 82.6) / 3.0;,System.out.println("Your grade was " + grade);
Increment and Decrement
- Shorthand:
variable++,variable-- - Equivalent longer version:
variable = variable + 1;,variable = variable - 1; - Example:
int x = 2;,x++;,xnow stores3
Modify-and-Assign
- Shorthand:
variable += value;,variable -= value;,variable *= value;,variable /= value;,variable %= value; - Equivalent longer version:
variable = variable + value;,variable = variable - value;,variable = variable * value;,variable = variable / value;,variable = variable % value; - Example:
x += 3;,gpa -= 0.5;
Java Operator Precedence
- Description: Unary operators, binary multiplicative operators, binary additive operators, assignment operators
- Operators:
++,--,+,-,*,/,%,=,+=,-=,*=,/=,%= - Binary operators in the same level (e.g.,
+and-) are of equal priority and are evaluated left to right - Unary operators in the same level (e.g.,
+and-) are of equal priority and are evaluated right to left - Assignment operators in the same level (e.g.,
=) are of equal priority and are evaluated right to left
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Description
Evaluate the expression z – (a + b / 2) + w * -y using the order of operations with given values of variables. Practice applying operator precedence rules to simplify expressions.
