Download Branching Statements

Catie Welsh
February 2, 2011
1

Program 1 Due Today by 11:59pm today

Program 2 Assigned Today

Lab 2 Due Friday by 1:00pm
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3

Formatting decimals

Review Worksheet

If/Else statements

Boolean Expressions
4

import java.text.*;

DecimalFormat df = new DecimalFormat("0.00");


df.format(myVariable);
Example code on class website
5
public class MyProgram
{
public static void main(String[] args)
{
String myString = “This is a string”;
int len = myString.length();
System.out.print(“the length is “ + len);
String shortString = myString.substring(10);
}
}
6

Double myDouble = (1 / 2) * 5.0;

int i = 1 / 2;
O
0.5
7

Suppose that mary is an object of class Person, and suppose
that increaseAge is a method of class Person that uses one
argument, an integer. Write the invocation of the method
increaseAge for the object mary using the argument 5.
Person mary = new Person;
mary.increaseAge(5);
8
9
Check time;
if (time < 7am)
{
take bus;
}
else //time >= 7am
{
take subway;
}
Reach school;
10
import java.util.*;
public class FlowChart
{
public static void main(String[] args)
{
System.out.println("Give me an integer:");
Scanner keyboard = new Scanner(System.in);
int inputInt = keyboard.nextInt();
Start
Prompt User for int
NO
Is user
input
greater
than 5?
Print: “small
number”
if( inputInt > 5)
{
System.out.println("Big number");
}
else
{
System.out.println("Small number");
}
YES
Print: “big
number”
}
}
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==
!=
>
>=
<
<=
Equal to
Not equal to
Greater than
Greater than or equal to
Less than
Less than or equal to
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

True of False
Example expressions
◦ 5 == 3;
◦ Variable <= 6;
◦ myInt != temp;

if (boolean expression)
{ statements }
13


What if you need multiple expressions to be
true
(expression) && (expression) && …
◦ Expressions go in ( )

Will only be true if ALL statements are true
14


What if you need ONE expression to be
true out of many expressions
(expression) || (expression) || …
◦ Expressions go in ( )

Will be true if ONE expression is true
15

FIGURE 3.7 The Effect of the Boolean
Operators && (and), || (or), and ! (not) on
Boolean values

var1 = var2
◦ Error!!!!!!!
(assignment statement)

var1 == var2 (boolean expression)

Do NOT use == to compare Strings
◦ string1 == string2
//BAD
◦ string1.equals(string2); //GOOD
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
Syntax
String.equals(Other_String)
String.equalsIgnoreCase(Other_String)


You can use just an if statement
if (boolean expression)
{ (statements) }
the rest of your code
19
if (boolean expression)
{
if (boolean expression)
{ stuff goes here }
else
{ more stuff }
}
else
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Start
Prompt User for int
inputInt == 0
What
is the
integer?
inputInt > 1
inputInt == 1
Print: “hello”
Print: “how are you”
Print: “how may I
help you”
21
import java.util.*;
public class FlowChart
{
public static void main(String[] args)
{
System.out.println("Give me an integer:");
Scanner keyboard = new Scanner(System.in);
int inputInt = keyboard.nextInt();
if ( inputInt == 0)
System.out.println(”hello");
else if ( inputInt == 1)
System.out.println(”how are you");
else
System.out.println(”how may I help you");
}
}
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
Recitation

Bring Laptop

Bring Book
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