• Homework Solution
• JUnit Testing
• Arrays
• Conditional Statements
• Control Flow

• In Eclipse:
• New > JUnit Test Case
• Select "OK" to add JUnit to the build path
• Test naming convention is to name the test case "MyClassTest.java" where "MyClass" is the Class you're testing.

• @Test tag designates a Test Unit
• Inside each test, use assert functions to compare an expected and actual value

 @Test
 public void addTest() {
     assertEquals(6, MyClass.add(3, 3);
 }

• Arrays contain an ordered set of values
• int [] arr = {1, 2, 3, 4, 5};
• An array created with values
• int [] arr2 = new int[50];
• An array declared with space for 50 ints.
• What is the default value of each upon initialization?

• Once created, the size of an array cannot be changed.
• To grow an array, copy values to a larger array.
• Example method to create an int array of dynamic size:

 public int [] createIntArray (int size) {
     return new int [size];
 }

• Typical Initialization and usage:

 String [] sa = new String[2];
 sa[0] = "String 0"; 
 sa[1] = "String 1";

 String [] sa = {"String 0", "String 1"};

• To achieve a 2 or 3 dimensional array, create arrays inside of arrays.

 int [] [] a = {{1,2}, {3,4}, {5,6}};
 System.out.println(a[1][0]);  //prints 3
 int [] [] b = new int [5][3]; b[0][2] = 5;

• Arrays are not primitive types.
• An array variable points to the array.
• An array argument in a method points to the passed array.

 public class Arrays {
     public static void main(String [] args) {
          int [] a = {10, 15, 0};
          add(a);
          System.out.println(a[2]);
     }
     public static void add(int [] arr) {
          arr[2] = arr[0] + arr[1];
     }
 } //a[2] prints as 25

• Array argument can be pointed to a new Array which does not affect original array.

 public class Arrays {
     public static void main(String [] args) {
          int [] a = {10, 15, 99};
          add(a);
          System.out.println(a[2]);
     }
     public void add(int [] a) {
          a = new int[3];
          a[2] = a[0] + a[1];
     }
 }
 //a[2] prints out 99, unaffected by the add function

• Runs certain code based on a set of true/false evaluations
• Common Conditional statements:
• if / else
• switch
• for
• while
• for each

• Only one path is executed
• Statement in parentheses must evaluate to true or false

 int a = 5;
 int b = 10;

 if (a == b) {
     System.out.println("same");
 } else if (b == a*2) {
     System.out.println("double");
 } else {
     System.out.println("different");
 }

• Switch statement tests a variable against several pre-defined cases, executing code if a match is found.
• Switches work with bytes, shorts, chars, ints, Enums, Strings and a few more.
• Break statement must be included after each case to stop the code execution

 int num = 4;
 switch(num) {
     case 3:
        System.out.println("Three");
        break;
     case 4:
        System.out.println("Four");
        break;
     default:
        System.out.println("Different");
 }

• Loops until a certain case evaluates to false
• Built in code execution at the end of each loop

 //count up 
 for(int i = 0; i < 10; i++) {
     System.out.println(i);
 }

 //count down
 for(int i = 10; i > 0; i--) {
     System.out.println(i);
 }

• Loops through an array or Collection
• More convenient than a full-blown for loop
• Left side of the colon is a declared variable for each element
• Right side is the collection

 int [] numArray = {1, 2, 3, 4, 5};
 for(int number : numArray) {
     System.out.println(number);
 }

• Loops until a statement evaluates to false

 //loops forever
 while(true) {
     System.out.println("Forever");
 }

 //loops 10 times
 int i = 0;
 while(i < 10) {
     System.out.println(i);
     i++;
 }

• Control flow statements change the execution of your program
• break
• Used to break out of a for/while loop or switch
• continue
• Used to skip to the next iteration of a for/while loop
• return
• Used to return from a method. 
• return can take a value to return back to the calling method.

• The break statement terminates the innermost for/while or switch statement.

 int [] numbers = {1, 2, 3, 4, 5};
 for(int num : numbers) {
     if(num ==3) {
          break;
     }
 }

• The return statement halts execution of the current method and returns control to the code where it was called.

 public static boolean hasNumber(int number, int [] numArray) {
     for(int arrNum : numArray) {
          if(arrNum == number) {
               return true;
          }
     }
     return false;
 }

• The continue statement skips the current iteration of a loop and continues to the next, for a for/while loop.

 int [] numbers = {1, 2, 3, 4, 5};
 for(int num : numbers) {
     if(num % 2 > 0) 
         continue;
     System.out.println(num + " is an even number");
 }