The Knowledge Of Sauron's Minions
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| − | + | [[image:Rivendell.jpg]] | |
| − | + | Welcome to Rivendell! You have completed your stay at Hogwarts and have come here to study Java even further, to learn the dark secrets of Sauron. | |
| + | ==(A) Revealing The Knowledge== | ||
| + | [[File:Robert As Gandalf.jpg|thumb|Gandalf speaking here...]] | ||
Sauron knows whatever his servants, the RingWraiths, know, thus it is essential to learn of the types of knowledge RingWraiths and other fell classes can possess. | Sauron knows whatever his servants, the RingWraiths, know, thus it is essential to learn of the types of knowledge RingWraiths and other fell classes can possess. | ||
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} | } | ||
</pre> | </pre> | ||
| − | There is only one method, main(), in this RingWraith class: the other statements at the beginning declare '''variables'''. The five variables here are the most frequently used sorts. | + | There is only one method, main(), in this RingWraith class: the other statements at the beginning declare '''variables'''. Variables are places where the program can remember information. You can think of them as like little boxes, or perhaps whiteboards where you can write and erase things you want to remember. The five variables here are the most frequently used sorts. |
There are many '''basic types''', but here we shall concern ourselves with only four. | There are many '''basic types''', but here we shall concern ourselves with only four. | ||
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Type '''String''' is not a basic type: it is a '''class''' and variables of type String are called '''objects'''. String is one of the important classes that come with Java, and one of the most frequently used classes. | Type '''String''' is not a basic type: it is a '''class''' and variables of type String are called '''objects'''. String is one of the important classes that come with Java, and one of the most frequently used classes. | ||
| − | ==Further Revellations== | + | ==(B) Further Revellations== |
# Trap the RingWraith code within Dr. Java. | # Trap the RingWraith code within Dr. Java. | ||
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# Brace-matching Color is tricky. How do you reveal it in the code? | # Brace-matching Color is tricky. How do you reveal it in the code? | ||
# I can hardly see the Type Color in the code. Click the ellipsis (...) button to the right of Type Color, and change the color to a dark red. Click Apply and OK. More visible now? | # I can hardly see the Type Color in the code. Click the ellipsis (...) button to the right of Type Color, and change the color to a dark red. Click Apply and OK. More visible now? | ||
| − | # '''Keyword''' means the same as '''reserved word'''. | + | # '''Keyword''' means the same as '''reserved word'''. Thou shalt prepare a litany (list) of these reserved words for the purposes of further study. |
# The basic types are also reserved words: what else then should we add to our list of reserved words? | # The basic types are also reserved words: what else then should we add to our list of reserved words? | ||
# Why shouldn't we add String to the reserved words? | # Why shouldn't we add String to the reserved words? | ||
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# The exception is boolean: '''true''' and '''false''' are reserved words. | # The exception is boolean: '''true''' and '''false''' are reserved words. | ||
| − | ==The Arcane Knowledge== | + | ==(C) The Arcane Knowledge== |
| − | + | # Add another variable to RingWraith, of type double and named "compute". | |
| − | + | # Inside main(), add 'compute = Math.sin(Math.PI/6);' | |
| − | + | # Print out the value of compute with the proper incantation. What have we wrought? | |
| − | + | # Look on my page for "References", and click on Math. Explore therein and find the secrets of exponentiation and other precalculus functions. | |
| + | |||
| + | ==(D) Multitudinous Variables== | ||
| + | As yet we have examined only singular variables. In mathematical lore, we often use variables that contain multitudes, as in matrices. In Java, we have row matrices, called '''arrays'''. Arrays can be of any type. We specify an array of a type by placing square brackets '[]' after the type. | ||
| + | * Add 'static public int[] anArray = {8, 2, 5};' to the variables at the top of RingWraith. | ||
| + | In math, we would express this as: | ||
| + | |||
| + | anArray = [8 2 5] | ||
| + | |||
| + | In math, we would use subscripts to specify which of the numbers to select, subscripts from 1 to 3. But '''in Java subscripts start at zero''' and '''subscripts are numbers within square brackets'''. Each number in an array is called an '''element'''. | ||
| + | # Add 'System.out.println( anArray[0] + anArray[1] + anArray[2] );' into main(). What does this do? | ||
| + | # You might notice that the array was initialized to three values by placing the set of values in curly braces. Where else have we used curly braces? | ||
| + | # What is element 2 of the array? | ||
| + | # Add another value to the array by putting another number within the curly braces. | ||
| + | # Change one of the array values by adding this line in main(): 'anArray[1] = -3;'. Can you write a set of println() to show all the array values, and see which has changed? | ||
| + | # Look ye at the signature of main(). Where is the array in it? What is it an array of? | ||
