Download ICS4U Java Syntax Name: Efficient If Statements Date: This Java

ICS4U
Java Syntax
Name:
Efficient If Statements
Date:
This Java code segment is correct, but terribly inefficient in terms of processing
speed, memory usage, and length. How can it be improved?
Scanner in = new Scanner(System.in);
System.out.println(“Amount over speed limit:”);
int overSpeedLimit = Integer.parseInt(in.nextLine());
int points = 0;
if ( overSpeedLimit >= 50 ) {
points = 6;
}
else if ( overSpeedLimit >= 30 ) {
points = 4;
}
else if (overSpeedLimit >= 16 ) {
points = 3;
}
System.out.println(points + “ demerit points!”);
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ICS4U

Java Syntax
Name:
Efficient If Statements
Date:
Avoid Unnecessary If Statements
This code segment has four separate if statements when it actually only needs
one
If it is possible for more than one branch to be applicable, then more than one if
statement should be used
If it is possible for only one branch to be applicable, then only one if statement
should be used

Do Not Check Conditions More Than Necessary
You learn a lot of information when an if statement condition is false.
Remember this information so that you don’t unnecessarily check it again

Factor Up
If the first line of code inside each branch is the same, then that line of code can be
factored up out of the if statement. Factoring up reduces the number of lines of
code without changing the program’s functionality

Factor Down
If the last line of code inside each branch is the same, then that line of code can be
factored down out of the if statement. Factoring down also reduces the number
of lines of code without changing the program’s functionality
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ICS4U
Java Syntax
Name:
Efficient If Statements
Date:
Here is the Java code segment rewritten for efficiency:
Scanner in = new Scanner(System.in);
System.out.println(“Amount over speed limit:”);
int overSpeedLimit = Integer.parseInt(in.nextLine());
int points = 0;
if ( overSpeedLimit >= 50 ) {
points = 6;
}
else if ( overSpeedLimit >= 30 ) {
points = 4;
}
else if ( overSpeedLimit >= 16 ) {
points = 3;
}
System.out.println(points + “ demerit points!”);
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ICS4U
Java Syntax
Name:
Efficient If Statements
Date:
Homework
Rewrite the Java programs below so that they are more efficient:
1. Admission to the Toronto Zoo
import java.util.*;
public class TorontoZoo {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int age, price = 0;
System.out.println(“How old are you?”);
age = Integer.parseInt(in.nextLine());
if ( age >= 65 )
{ price = 14; }
else if (age >= 13 ) { price = 20; }
else if (age >= 4 )
{ price = 12; }
System.out.println(“Ticket price $” + price);
}
}
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ICS4U
Java Syntax
Name:
Efficient If Statements
Date:
2. Long Distance
import java.util.*;
public class LongDistance {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String country;
System.out.println(“Where are you calling?”);
country = in.nextLine();
if ( country.equals(“Belgium”) ) {
double rate;
rate = 0.02;
System.out.println(“$” + rate + “ per min”);
}
if ( country.equals(“Cuba”) ) {
double rate;
rate = 1.20;
System.out.println(“$” + rate + “ per min”);
}
if ( country.equals(“Greenland”) ) {
double rate;
rate = 0.67;
System.out.println(“$” + rate + “ per min”);
}
if ( country.equals(“Peru”) ) {
double rate;
rate = 0.10;
System.out.println(“$” + rate + “ per min”);
}
}
}
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ICS4U
Java Syntax
Name:
Efficient If Statements
Date:
3. Gender Greetings
import java.util.*;
public class GenderGreetings {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println(“(m)ale or (f)emale?”);
String gender = in.nextLine();
System.out.println(“What is your last name?”);
String lastName = in.nextLine();
if ( gender.equals(“m”) )
{
System.out.println(“Hello Mr. ” + lastName);
}
else
{
System.out.println(“Hello Ms. ” + lastName);
}
}
}
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