1. ./AccountCheck.java
2. ./ArrayLength.java
3. ./ArraysExample.java
4. ./ArrayVars.java
5. ./CommandLineArgs.java
6. ./Countdown.java
7. ./Equals.java
8. ./StringConditionals.java

/**
 * This class demonstrates control flow in Java
 *
 * @author Sara Sprenkle
 *
 */
public class AccountCheck {  
    
    /* Alternatively, could make the variable have a "class-level" scope
    instead of just being within the method. 
    Probably not appropriate for this problem, but may be appropriate
    in other cases.
    
    static boolean approved = false;
    */
    
   /**
    * Called when user runs 
    *  java AccountCheck
    */
    public static void main(String[] args) {
        int purchaseAmount = 700;
        int availableCredit = 500;
        
        if (purchaseAmount < availableCredit) {
            availableCredit -= purchaseAmount;
            /* scope of variable is within this block of code
             and cannot be seen outside of this block. */
            boolean approved = true;
            approved = true;
        }

        if( ! approved ) 
            System.out.println("Denied");
    }
}

/**
 * This class demonstrates use of "length" field for arrays and the foreach
 * loop.
 *
 * @author Sara Sprenkle
 *
 */
public class ArrayLength {  
    
   /**
    * Called when user runs 
    *  java ArrayLength
    */
    public static void main(String[] args) {
        int[] array = new int[10];
        for (int i = 0; i < array.length; i++) { 
            array[i] = i * 2; 
        }

        for (int i = array.length -1; i >= 0; i--) {
            System.out.println(array[i]); 
        }
        
        // alternative for loop to iterate through the array
        for( int element : array ) {
            System.out.println(element);
        }
        
    }
    
}

// import the Arrays class so that we can use its functionality
import java.util.Arrays;

/**
 * This class demonstrates using arrays and the Arrays class
 *
 * @author Sara Sprenkle
 *
 */
public class ArraysExample {  
    
   /**
    * Called when user runs 
    *  java ArraysExample
    */
    public static void main(String[] args) {
        double[] array = new double[10];
        
        // fill the array with PI...  mmm... pie... using the Arrays class
        Arrays.fill(array, Math.PI);
        
        for( int i=0; i < array.length; i++ ) {
            System.out.println("array[" + i + "] = " + array[i]);
        }
    }
}

/**
 * Demonstrates that assigning an array variable to another variable
 * does *not* make a copy of an array.  Both variables are
 * referencing the same array.
 * @author CSCI209
 */
public class ArrayVars {
    
    public static void main(String[] args) {
        int [] fibNums = {1, 1, 2, 3, 5, 8, 13};
        int [] otherFibNums;
        
        otherFibNums = fibNums;
        otherFibNums[2] = 99;
        
        System.out.println(otherFibNums[2]);
        System.out.println(fibNums[2]);
    
        // Each statement above will output 99.  Why?
    }

}

/**
 * Example demonstrates use of command-line arguments
 */
public class CommandLineArgs {

    public static void main(String[] args) {
        if( args.length < 1 ) {
            System.out.println("Error: invalid number of arguments");
            System.exit(1);
        }
        
        // use the argument ...
        System.out.println("First argument is: " + args[0] );
        
        for(int i = 0; i < args.length; i++ ) {
            System.out.println(args[i]);   
        }
    }

}

/**
 * This class demonstrates a counting for loop
 *
 * @author Sara Sprenkle
 *
 */
public class Countdown {  
    
    public static void main(String[] args) {
        System.out.println("Counting down...");

        for (int count=5; count >= 1; count--) {
            System.out.println(count);
        }
        System.out.println("Blastoff!");
    }
}

/**
 * Demonstrates different equals with Strings
 * Run as
 *   java Equals <command-line argument>
 * @author Sara Sprenkle
 */
public class Equals {

    public static void main(String args[]) {
        String string1 = "same";
        String string2 = string1;
        // The following statement doesn't create a _new_ String object/memory 
        // allocation Java memory optimization
        String string3 = "same"; 
        String string4 = args[0]; //enter "same" as a command-line argument
        //String string4 = "same"; //for first half of lecture
        
        System.out.println("string1 == string2? " + (string1==string2));
        System.out.println("string2 == string3? " + (string2==string3));
        System.out.println("string1 == string4? " + (string1==string4));
        // output should be
        // true
        // true
        // false, regardless of what user enters
        
        System.out.println("string1 equals string2? " + (string1.equals(string2)));
        System.out.println("string2 equals string3? " + (string2.equals(string3)));
        System.out.println("string1 equals string4? " + (string1.equals(string4)));
        
        // output should be
        // true
        // true
        // true (depending on what user enters)
    }

}

/**
 * Example using methods in conditionals.
 * Enter "same" as command-line argument to guess the string.
 * 
 * @author Sara Sprenkle
 */
public class StringConditionals {

    public static void main(String args[]) {
        String string1 = "same";
        
        if( args.length < 1 ) {
            System.out.println("Error: invalid number of arguments");
            System.out.println("Usage: java StringConditionals <guess>");
            System.exit(1);   
        }
        
        String argString = args[0];
        
        if( string1.equals(argString) ){
            System.out.println("You guessed my string!");
        } else {
            System.out.println("Nice try, but you didn't guess my string.");
        }
        
    }

}