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dish, directive installerLet us pretend to be a nurse. (Medical insurance is so high that you don't want to be sick. So do exercsises!) You take kids ear temperature to see if they have fever or not. If thermometer reading is greater than 100.4, you print out "Beep, Beep, Beep!", other wise you print out "No fever".

Since a nurse could take a lot of temperature. We also don't want to define a lot of double variables in our code. Instead, we use only one variable to store the temperature reading.

I will show you one trick: accept ear temperature reading from command line.

Take parameters from command line

When we try to run a program, we type in command line: java program.

If you type: java program arg0 arg1 arg2 arg3 arg4...., JAVA boy will transfer arg0 arg1 arg2 arg3 arg4... into main method.

public static void main(String[] args)

See? All you typed arg0 arg1 arg2 arg3 arg4.. will be in the array String[] args. Remember, JAVA boy counts everything start from 0.

Here is our thermometer code:

class thermometer
{
public static void main(String[] args)
{
   double temperature;
   temperature=Double.parseDouble(args[0]);
   if(temperature>100.4)
      System.out.println ("Beep Beep Beep");
   else
      System.out.println("No fever.");
}
}

Save the above code as thermometer.java. Compile it: javac thermometer.java. Then run: java thermometer 102.3. 102.3 is the temperature. In the code, args[0]="102.3". Double.parseDouble is new thing to you. It converts a string to a double value. Double is a class and parseDouble is its method. It is just one handy tools JAVA boy provides.

Try type: java thermometer abc

What did you see? Look like the following? I will answer you in class 9.

Exception in thread "main" java.lang.NumberFormatException: For input string: "abc"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1224)
at java.lang.Double.parseDouble(Double.java:482)
at thermometer.main(thermometer.java:8)

 

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Professional Java, JDK 5 Edition (Paperback Simply Java Programming: An Application-Driven Tutorial Approach (Paperback) Effective Java Programming Language Guide (Paperback) Head First Java, 2nd Edition (Paperback) Java : An Introduction to Problem Solving and Programming (4th Edition)

 

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