Lab 3: Programming in java

Assignment due on Thursday, May 29

In the previous lab, we have setup Eclipse, and written our first Java program that printed "Hello world" to the console screen. Today, we will build on our knowledge and experiment the concepts we learnt in class.

1. Start Eclipse and open your previously created project. If you haven't created a project in the last class, you can see how to do it here
2. Experiments with data types
   • Declare several variables with different types

     Example:
     public static void main(String[] args)
     {
       int x;
       double y;
       int a,b,c;
       String s1;
         ...
     }
     

   • Try declaring some variables with assigned values

     Example:
     String s2 = "This one contains a default value";
     

   • Keep in mind that you must end all instructions with a semi-colon. What will happen if you won't end with one?
   • Also keep in mind the identifier rules. Can you try to declare a variable not satisfying the rule?
   • Where have you declared your variables? In the main function? Or outside it? Try doing both. Does eclipse give you an error?
   • What is the maximum value each data type can get? What if you assign a value that is higher than that?
   • Try the unsigned keyword

     Example:
     unsigned int x;
     

3. Experiments with operators
   • Change the value of your declared variables

     Example:
     int x;
     String s2= "This one contains a default value";
     ...
     x=1130;
     String s2= "Now I have changed the content";
     

   • Get yourselves familiar with the arithmetic, logical and relational operators. (You can try the examples from the slides)
4. Experiments with control statements
   • So far, we have been using sequential control statements. Now let's try the other statements. We have learnt in class that operators have a precedence order. Try to test them in an if-else selection statement.

     Example:
     int x=10,z=12,y=30;
     if(x==z-2||3>2&&y%10!=2)
     {
       System.out.println("Statement is true");
     }
     else
     {
       System.out.println("Statement is false);
     }
     

   • Switch case statement: Copy and paste the following code and run it. What is it doing?

     String name;
     try{
       System.out.print("Enter your first name: ");
       java.io.DataInputStream in = new java.io.DataInputStream(System.in);
       name = in.readLine();
       int nameNumber=0;
       if(name.equals("Eriks")
     	nameNumber = 1;
       else if(name.equals("Amanda")
     	  nameNumber = 2;
     	  else if(name.equals("Jennifer")
     	         nameNumber = 3;
       switch(nameNumber)
       {
         case 1:System.out.println("Hello Mr.Reks");break;
         case 2:System.out.println("Hello Ms.Patterson");break;
         case 3:System.out.println("Hello Ms.Wei");break;
         default: System.out.println("I'm sorry I don't know you. Please enter your last name:");
                  String last_name=in.readLine();
                  System.out.println("Hi "+name+" "+last_name);
       }
     }
     catch(Exception e)
     {
       System.out.println("I'm sorry. Something extraordinary happened and your program terminated!");
     }
     

   • Simple sorting algorithm. Implement the following algorithm in java

       Declare integers a,b,c,d;
       Assign values into a, b, c, and d
       Do the following steps 4 times:
         Let I = 1
         While (I < 4) do the following:
           If the Ith number in the list is greater than the I+1st, then:
             Swap the Ith and I+1st numbers in the list.
           Add 1 to I
       Print out the list.
     

5. Assignment(to do at home): Using precise English, and writing for someone who can do basic arithmetic, but who has no common sense at all, write an algorithm to make (monetary) change. Your algorithm should expect an input value that represents some amount of money in cents and give as output the number of quarters, dimes, nickels, and pennies that together represent the amount of money given as input. You should use as many large denomination coins as possible before using any coins of a smaller denomination. Example: given an input of "31" cents, the algorithm should return "1 quarter, 1 nickel, and 1 penny".
   • To input a number from keyboard(like we did with the example with names) use readInt() function, instead of readln().
   • You will need to implement the monetary change assignment in a new project. Name the project "Monetary change" and name your program "lab3.java"

Save what you have done today in your P: drive (or H:). In this case, you can access your files from Webfiles at home(You will need the examples as a reference manual to finish your assignment).