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

/**
 * This class demonstrates scope and control flow in Java.
 *
 * @author Sara Sprenkle
 *
 */
public class AccountCheck {  
    
   /**
    * Called when user runs 
    *  java AccountCheck
    */
    public static void main(String[] args) {
        int purchaseAmount = 700;
        int availableCredit = 500;
        
        boolean approved = false;

        if (purchaseAmount < availableCredit) {
            availableCredit -= purchaseAmount;
            /* scope of following declared variable 
             is within this block of code
             and cannot be seen outside of this block. 
             boolean approved = false;
             */
            approved = true;
        }

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

/**
 * This class demonstrates use of "length" field for arrays
 * as well as for loops 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 = array.length -1; i >= 0; i--) {
            System.out.println(array[i]); 
        }
        
        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?
        
        int x = 1;
        // This will display fibNums[1]
        System.out.println(fibNums[x++]); 

        x = 1;
        // This will display fibNums[2]
        System.out.println(fibNums[++x]);
        
  
        System.out.println(otherFibNums == fibNums);
        
        String[] myArgs = args;
        System.out.println(myArgs == args);
    }

}

/**
 * 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!");
    }
}

/**
 * This class demonstrates using a while loop
 *
 * @author Sara Sprenkle
 */
public class Counter {  
    
    public static void main(String[] args) {
        int counter = 0;
        while (counter < 5) {
            System.out.println(counter);
            counter++;
        }
        System.out.println("Done: " + counter);
    }
}

/**
 * Demonstrates how various checks of 
 * equality work 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 = "same"; //for initial discussion
        String string4 = args[0]; //enter "same" as a command-line argument

        
        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)
    }

}

/**
 * This class demonstrates using a switch statement.
 * 
 * Your task: Explain the output when grade is set to be 'b'
 * and then when grade is set to 'd'.
 *
 * @author Sara Sprenkle
 *
 */
public class Grades {  
    
   /**
    * Called when user runs 
    *  java Grades
    */
    public static void main(String[] args) {
        char grade = 'b';
        
        switch(grade) {
            case 'a':
            case 'A':
                System.out.println("Congrats!");
                break;
            case 'b':
            case 'B':
                System.out.println("Not too shabby!");
                break;
            case 'c':
            case 'C':
            case 'd':
            case 'D':
                System.out.println("You are passing but you could improve.");
            case 'f':
            case 'F':
                System.out.println("Not good.  You failed.");
            default:
                System.out.println("Error: not a grade");
        }
    }
}

/**
 * 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];
        
        // this can never be true 
        if( string1 == argString) {
            System.out.println("Exact match!");
        }
        else if (string1.equals(argString) ){
            System.out.println("You guessed my string!");
        } else {
            System.out.println("Nice try, but you didn't guess my string.");
        }
        
    }

}