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ECCE Exercises 1: Software development Predict the outcomes of the following programs and write them in your logbook. You will need to use your textbook for anything which isn't obvious or which you can't make a logical guess about. Then type the programs in, compile and run them. Unlike the very first Hello program, you run most of these programs by typing parameters (in bold in the exercises) on the command line after the filename of the Java class. Programs can then read these parameters and use them as input. Input is quite hard in Java, so in the beginning, getting input via the command line, as in these programs, is the simplest way. Write down the results and why your predictions were right or wrong in your logbook. Note that some programs might have syntax errors that you need to correct first! __________________________________________________________ Hello.java // Text-printing program class Hello { public static void main (String[] args) { System.out.println("Hello!"); } // end method main } // end class Hello __________________________________________________________ Hello1.java class Hello1 { public static void main(String[] args) { System.out.println("Hello "+ args[0] + "!" ); } // of main } // of class Hello1 Compile and then run by typing: C\jwork\myprogs> java Hello1 Jerry Maguire (assuming your programs are in C:\jwork\myprogs) __________________________________________________________ Hello2.java class Hello2 { public static void main(String[] args) { String student = "I am a student"; System.out.println("Hello, "+ Student + "!" ); } // of main } // of Hello2 No parameters this time, just type C\jwork\myprogs> java Hello2 ___________________________________________________________ Salary.java class Salary { public static void main(String args[]) { int salary = 50; salary = salary * 5; System.out.println("The weekly salary is £" + salary); } // of Salary C\jwork\myprogs> java Salary 300 Updated 26/09/05 1 ECCE ___________________________________________________________ Root.java class Root { public static void main(String args[]) { int number = 0; number = Integer.parseInt( args[0] ); System.out.println("The square root of " + number + " is " + Math.sqrt(number) ); } // of main } // of Root C\jwork\myprogs> java Root 263 ___________________________________________________________ Programming assignments (for lab and postlab activity) Now some new exercises for you to try, but first, study the 'arguments.java' program - this will be a great help. i) Write a Java program (Repeat.java) to print out all the words you typed in the command line, e.g. C\jwork\myprogs> java Repeat this is a test should produce the output below: 'this is a test' ii) Write a Java currency converter program (e.g. from pounds to Euros), where the amount in pounds is entered on the commend line. iii) Write a Java program to find the average of all the numbers entered on the command line. iv) Modify the Salary program above so that it really does take the daily salary you enter on the command line and use it to print out a weekly salary. v) Run the Hello1 program without entering any parameters on the command line. Just record what happens and see if you can make sense of the Java messages you get. vi) Modify the Hello program by using the class Scanner. All these exercises should be carefully written up in your logbook. Listings should be written into or stuck into to your logbook, never kept loose. You should also write down exactly what happened as you were compiling and running the programs. One of the roles of a logbook is to keep a factual record of tests done - without this, developing quality software is impossible. Updated 26/09/05 2