1. Chapter 3 Assignment Statement
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Chapter 3 Assignment Statement
An assignment statement gives a value to a variable.
Assignment can take several forms:
x = 5; a literal (5) is assigned to x
x = y + 2; the value of an expression (y + 2) is assigned to x
x = z; the value of another variable (z) is assigned to x
Assignment requires an equal sign (=). The value on the right is "given to" or "assigned" the value of the variable on the left.
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2. Chapter 3 Variable Assignment
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Chapter 3 Variable Assignment
A variable can store only one value at any time.
int x;
x = 5;
x = 10; x 10 5
Note: This slide contains animations. Press the space bar or click the mouse button to display each animation.
This slide contains three (3) animations.
The variable declaration, int x, associates the variable name x with a memory location <press space bar>
The first assignment statement, x = 5, associates the memory location for x with the value 5 <press space bar>
The second assignment statement, x = 10, associates the memory location for x with the value 10 <press space bar>
Note that once the variable x is associated with a new value, in this case 10, the previous value, 5, cannot longer be accessed.
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3. Chapter 3 Primitive Data Types
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Chapter 3 Primitive Data Types
Type Storage Required
int 4 bytes
double 8 bytes
char 2 bytes
boolean 1 bit
It is important to choose the appropriate data type when declaring variables so that the compiler allocates only the needed storage space for a variable. For example, declaring every variable a double will ensure that both ints and doubles can be represented, but unneeded storage space will be used. Additionally, the reader of the application will not be clear on what type of value a variable is expected to hold.
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4. Chapter 3 Abstract Data Types
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Chapter 3 Abstract Data Types
A variable declared with a class is called an object. For example, the object spot is type Circle:
Circle spot = new Circle(4);
spot
getRadius()
area()
Note: This slide contains animations. Press the space bar or click the mouse button to display each animation.
This slide contains one (1) animation.
The instantiation of object spot creates a reference to the object's data and method. <press space bar>
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5. Numerous packages are included with JDK Packages contain classes
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Chapter 3 Java Packages
Numerous packages are included with JDK
Packages contain classes
Packages can be added to an application with an import statement. For example, the statement import java.util.Scanner; makes the Scanner class and its methods accessible to the application.
Packages are reusable units of code that can be added to an application. An asterisk (*) can be used in place of a class name to import all the classes of a package.
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6. Chapter 3 The Scanner Class
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Chapter 3 The Scanner Class
Part of the java.util package
A Scanner object processes text and numbers from the input stream
Methods include:
next()
nextLine()
nextInt()
nextDouble()
nextBoolean()
close()
The Scanner class is used to read input from the user.
The Scanner method that should be used depends on the data expected from the user.
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7. Chapter 3 Integer Division
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Chapter 3 Integer Division
Integer division (/) is performed when both operands are integers. Only the integer portion of the quotient is returned:
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8. 9/8/ :43 AM
Chapter 3 Real Division
Real division (/) is performed when one or both operands are type double. The entire quotient, including the decimal portion is returned:
double result;
result = 20.0/7.0; //result is 2.857
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9. Chapter 3 Modulus Division
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Chapter 3 Modulus Division
Modulus division (%) returns the remainder of a division operation:
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10. Chapter 3 Operator Precedence
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Chapter 3 Operator Precedence
Operators in Java have the following precedence:
1. multiplication and division
2. addition and subtraction
Operators of the same precedence are evaluated in order from left to right. For example, multiplication is performed first, then division, and finally addition:
5 + 6 * 4 / 2 = 17
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11. Chapter 3 Changing the Order of Operations
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Chapter 3 Changing the Order of Operations
The order in which operators are evaluated can be changed by using parentheses. For example, addition is performed first, then multiplication, and finally division:
(5 + 6) * 4 / 2 = 22
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12. 9/8/ :43 AM
Chapter 3 Type Casting
Type Casting converts a number of one type to a number of a different, but compatible type. Type casting is used to:
1. make the operand types in an expression match. For example, wholeNum = (int)y * 2
2. truncate the decimal portion of a double. For example, wholeNum = (int)z
3. change the way in which a division (/) operation will be performed. For example, realDivision = (double)a / (double)b
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13. Chapter 3 Assignment Operators
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Chapter 3 Assignment Operators
Operator Operation
+= addition and then assignment
-= subtraction and then assignment
*= multiplication and then assignment
/= division and then assignment
%= modulus division and then assignment
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14. Chapter 3 Named Constants
A named memory location that cannot be changed from its initial value.
The keyword final is used in a constant declaration.
Constant identifiers are typically all uppercase with an underscore (_) separating words within the identifier name.
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15. Chapter 3 Java Keywords abstract double int strictfp boolean else
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Chapter 3 Java Keywords
abstract
double
int
strictfp
boolean
else
interface
super
break
extends
long
switch
byte
final
native
synchronized
case
finally
new
this
catch
float
package
throw
char
for
private
throws
class
goto
protected
transient
const if
public
try
continue
implements
return
void
default
import
short
volatile do
instanceof
static
While
Keywords have special meaning to the Java compiler and therefore cannot be used for a variable or constant identifier.
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16. Chapter 3 Programming Errors
Syntax errors violate the rules of Java.
Logic errors, also called semantic errors, occur in statements that are syntactically correct, but produce undesired or unexpected results.
Run-time errors, also called exceptions, halt program execution at the statement that cannot be executed. One type of exception is called InputMismatchException.
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