Week 4 -Wednesday
What did we talk about last time? if and else examples Pitfalls
Assume that you have a variable called base of type char Let base contain one of: 'A' , 'C' , 'G' , 'T' Write a series of if - and else -statements that will print out the chemical name of the base denoted by the corresponding character A -> Adenine C -> Cytosine G -> Guanine T -> Thymine
if( base == 'A' ) System.out.println("Adenine"); else if( base == 'C' ) System.out.println("Cytosine"); else if( base == 'G' ) System.out.println("Guanine"); else if( base == 'T' ) System.out.println("Thymine"); else System.out.println("Your base doesn't belong to us"); What if you want to take care of upper and lower cases?
if( base == 'A' || base == 'a' ) System.out.println("Adenine"); else if( base == 'C' || base == 'c' ) System.out.println("Cytosine"); else if( base == 'G' || base == 'g' ) System.out.println("Guanine"); else if( base == 'T' || base == 't' ) System.out.println("Thymine"); else System.out.println("Your base doesn't belong to us"); Is there a simpler way?
base = Character.toUpperCase( base ); if( base == 'A' ) System.out.println("Adenine"); else if( base == 'C' ) System.out.println("Cytosine"); else if( base == 'G' ) System.out.println("Guanine"); else if( base == 'T' ) System.out.println("Thymine"); else System.out.println("Your base doesn't belong to us");
But, didn't that DNA example seem a little clunky? Surely, there is a cleaner way to express a list of possibilities Enter: the switch statement
switch( data ){ case value1: statements 1; case value2: statements 2; … case valuen: statements n; default: default statements; }
switch( base ) { case 'A': System.out.println("Adenine"); break; case 'C': System.out.println("Cytosine"); break; case 'G': System.out.println("Guanine"); break; case 'T': System.out.println("Thymine"); break; default: System.out.println("Your base doesn't " + "belong to us"); break; // unnecessary }
Both "Three" int data = 3; and "Four" switch( data ) { are printed case 3: System.out.println("Three"); case 4: System.out.println("Four"); break; case 5: System.out.println("Five"); The } break is The default optional is optional too
1. The data that you are performing your switch on must be an int , a char , or a String 2. The value for each case must be a literal 3. Execution will jump to the case that matches 4. If no case matches, it will go to default 5. If there is no default , it will skip the whole switch block 6. Execution will continue until it hits a break
switch( base ) { case 'A': case 'a': System.out.println("Adenine"); break; case 'C': case 'c': System.out.println("Cytosine"); break; case 'G': case 'g': System.out.println("Guanine"); break; case 'T': case 't': System.out.println("Thymine"); break; default: System.out.println("Your base doesn't " + "belong to us"); break; // unnecessary }
Using if -statements is usually safer if -statements are generally clearer and more flexible switch statements are only for long lists of specific cases Be careful about inconsistent use of break
Write a program that reads in various ages and prints out any special abilities you gain at that age 16 Drive a car 17 Watch R-rated movies 18 Vote and smoke 21 Drink 25 Rent cars 30 Be a senator 35 Be president
Anniversary Traditional Anniversary Traditional Write a program 1st Paper 10th Tin or Aluminum that reads in 2nd Cotton 20th China wedding 3rd Leather 25th Silver anniversaries and 4th Fruit or Flowers 30th Pearl 5th Wood 35th Coral gives the 6th Candy or Iron 40th Ruby traditional gift for 7th Wool or Copper 45th Sapphire that anniversary 8th Pottery or Bronze 50th Gold 9th Willow or Pottery 60th Diamond
Write a program that will read in a positive integer and print out the corresponding ordinal number Number Ordinal Number Ordinal 1 1st 11 11th 2 2nd 12 12th 3 3rd 13 13th 4 4th 21 21st 5 5th 22 22nd 6 6th 23 23rd
Review for Exam 1
Study for Exam 1 Monday, online, during class time Keep working on Project 2 Never look at another student's code
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