comp 14: switch, developing programs june 2, 2000 nick vallidis
Post on 19-Dec-2015
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TRANSCRIPT
Review
How does the do loop work?
How does the for loop work?
do
statement;
while (condition);
for (initialization; condition; increment)
statement;
Review (cont.)
What are the 4 ways to decrement a variable?
What's the difference between ++i and i++?
switch
The switch statement format:switch (expression){
case exp1:statement1;break;
case exp2:statement2;break;
default:statement;
}
switch
The switch statement format:switch (expression){
case exp1:statement1;break;
case exp2:statement2;break;
default:statement;
}
Java
reserved
words
switch
The switch statement format:switch (expression){
case exp1:statement1;break;
case exp2:statement2;break;
default:statement;
}
The expression is evaluated and control jumps to the case whose value matches. If there is no matching case, then control goes to default
switch
The switch statement format:switch (expression){
case exp1:statement1;break;
case exp2:statement2;break;
default:statement;
}
The statements are executed starting from the corresponding case until it gets to a break. At a break, control jumps to the end of the switch
switch
The switch statement format:switch (expression){
case exp1:statement1;
case exp2:statement2;break;
default:statement;
}
But the break statements are optional, so you could just run on to the next case if you leave it out
switch example
// i is a character the user typed inswitch(i){
case ‘a’:case ‘A’:
System.out.println("You entered 0");case ‘Z’:
System.out.println("You entered 1");default:
System.out.println("You entered " +"something other than 0 or 1");
}
comments on switch
only works with integral types (any primitive type except boolean or the floating point types)
This is basically an equality test
Developing programs
The book describes for basic steps establishing the requirements creating a design implementing the code testing the implementation
Developing programs
For the small code fragments we've done in class, we've gone straight for the implementation
For the rest of your assignments, it will really help you to go through this process
Establishing requirements
Here are the requirements: read in two names greet the users read in the day of the month that each of the
people was born report winner as person born earlier in month if it's a tie, report that it's a tie
Anything else?
Creating a design
We'll start by breaking it down into manageable steps: 1) ask for players' names 1.5) greet users 2) ask for players' days of birth 3) determine winner (or that it's a tie) 4) print out result
Creating a design
Then we can either break things down again if they're still big tasks, or get down to writing specifics.
This is simple enough that we'll go to specifics next.
Exciting new term!
pseudocode - a mixture of programming statements and English
Example:if class is over
everyone can leaveelse
everyone stays
2) ask for day of birth
ask (first name) for day of birthread in day of birthask (second name) for day of birthread in day of birth
3) determine winner
if (days of birth are equal)it's a tie
else{
if (person 1's day < person 2's day)person 1 was born first
elseperson 2 was born first
}
if (days of birth are equal)print it's a tie
else{
if (person 1's day < person 2's day)print person 1 was born first
elseprint person 2 was born first
}
4) print out result
Turns out that it's easier to combine 3&4
PB&J requirements
what you have: robot w/ 2 arms, jar of PB, jar of J, 2
slices of bread, 1 knifewhat you have to do:
make PB&J sandwichrobot can only take simple
instructions
So now we have 1 level...
Now break down each of these tasks into their steps.
Repeat this until you get down to steps you know how to program!
A well-known algorithm
Maybe you've seen this before? Lather Rinse Repeat
What's wrong with this as an algorithm?
Assignment P3
Here's the order you should probably try to do things: Get the framework going - announcing the
game, asking name, etc. make the higher-lower game work once.
(don't worry about checking for valid input) add the "do you want to play again?" loop add checking for valid input do the extra credit
Opening existing projects
Some people have had trouble with getting their programs to run after they quit Visual J++
2 of the ways to do this: (if it's your machine) go to the File menu and
right above exit will be the names of recent projects
click on my computer and keep going through folders till you get to the right one and double-click on <project name>.sln