1. if-else-if Statements
if-else-if statements can become very complex.
Imagine the following decision set.
if it is very cold, wear a heavy coat,
else, if it is chilly, wear a light jacket,
else, if it is windy wear a windbreaker,
else, if it is hot, wear no jacket.
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

2. if-else-if Statements
if (expression)
statement or block
else
// Put as many else ifs as needed here
Care must be used since else statements match up with the immediately preceding unmatched if statement.
Example: TestResults.java
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

3. if-else-if Flowchart
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

4. Nested if Statements
If an if statement appears inside of another if statement (single or block) it is called a nested if statement.
The nested if is only executed if the if statement it is in results in a true condition.
Nested if statements can get very complex, very quickly.
Example: LoanQualifier.java
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

5. Nested if Statement Flowcharts
“...you must have
been on job 2 years…”
Yes
Salary >=
30000?
“You must earn
at least…”
yearsOnJob
>= 2
“You qualify.... No
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

6. if-else Matching if (employed == 'y') This else { matches with this
if (recentGrad == 'y')
System.out.println("You qualify for the special interest rate."); }
else
System.out.println("You must be a recent college graduate to qualify.");
System.out.println("You must be employed to qualify.");
This else
matches
with this
if.
This else
matches
with this
if.
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

7. Logical Operators
Java provides two binary logical operators (&& and ||) that are used to combine boolean expressions.
Java also provides one unary (!) logical operator to reverse the truth of a boolean expression.
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

8. Logical Operators Operator Meaning Effect && AND
Connects two boolean expressions into one. Both expressions must be true for the overall expression to be true. || OR
Connects two boolean expressions into one. One or both expressions must be true for the overall expression to be true. It is only necessary for one to be true, and it does not matter which one. !
NOT
The ! operator reverses the truth of a boolean expression. If it is applied to an expression that is true, the operator returns false. If it is applied to an expression that is false, the operator returns true.
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

9. The && Operator
The logical AND operator (&&) takes two operands that must both be boolean expressions.
The resulting combined expression is true iff (if and only if) both operands are true.
Example: LogicalAnd.java
Expression 1
Expression 2
Expression1 && Expression2
true
false
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

10. The || Operator
The logical OR operator (||) takes two operands that must both be boolean expressions.
The resulting combined expression is false iff (if and only if) both operands are false.
Example: LogicalOr.java
Expression 1
Expression 2
Expression1 || Expression2
true
false
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

11. The ! Operator The ! operator performs a logical NOT operation.
If an expression is true, !expression will be false.
if (!(temperature > 100))
System.out.println(“Below the maximum temperature.");
If temperature > 100 evaluates to false, then the output statement will be run.
Expression 1
!Expression1
true
false
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

12. Order of Precedence Order of Precedence Operators Description 1
(unary negation) !
Unary negation, logical NOT 2
* / %
Multiplication, Division, Modulus 3
+ -
Addition, Subtraction 4
< > <= >=
Less-than, Greater-than, Less-than or equal to, Greater-than or equal to 5
== !=
Is equal to, Is not equal to 6
&&
Logical AND 7 ||
Logical NOT 8
= += -=
*= /= %=
Assignment and combined assignment operators.
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

13. Comparing String Objects
In most cases, you cannot use the relational operators to compare two String objects.
Reference variables contain the address of the object they represent.
Unless the references point to the same object, the relational operators will not return true.
Example: StringCompare.java
Example: StringCompareTo.java
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

14. Ignoring Case in String Comparisons
In the String class the equals and compareTo methods are case sensitive.
In order to compare two String objects that might have different case, use:
equalsIgnoreCase, or
compareToIgnoreCase
Example: SecretWord.java
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

15. void Methods and Value-Returning Methods
A void method is one that simply performs a task and then terminates.
System.out.println(“Hi!”);
A value-returning method not only performs a task, but also sends a value back to the code that called it.
int number = Integer.parseInt(“700”);
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

16. Two Parts of Method Declaration
header
public static void displayMesssage() {
System.out.println(“Hello”); }
body
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Chapter 5 Slide #16
Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

17. Parts of a Method Header
Method Modifiers
Return Type
Method Name
Parentheses
public static void displayMessage () {
System.out.println(“Hello”); }
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

18. Passing 5 to the displayValue Method
public static void displayValue(int num) {
System.out.println(“The value is “ + num); }
The argument 5 is copied into the parameter variable num.
The method will display The value is 5
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Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis

19. Passing Multiple Arguments
showSum(5,10);
public static void showSum(double num1, double num2) {
double sum; //to hold the sum
sum = num1 + num2;
System.out.println(“The sum is “ + sum); }
The argument 5 is copied into the num1 parameter.
The argument 10 is copied into the num2 parameter.
NOTE: Order matters!
Copyright © 2005 Pearson Addison-Wesley. All rights reserved.
Starting Out With Java 5
Control Structures to Objects
By Tony Gaddis