Methods & Conditionals

What if...

By NaughtySpirit Academy

Quick reminder

  1. What is Java & Android Studio?
     
  2. What is a variable? A variable has... ?
     
  3. Variable data types in Java?
     
  4. "4.0" + "4.0" = ? "4" + '4' ? 
     
  5. int a = "4.0" + 4? String a = "4.0" + 4?

NaughtySpirit Academy

Weekly test time

http://goo.gl/forms/9CyzS8GIl9

Today's content

  1. Projects
  2. What are conditionals?
  3. The If operator
  4. Comparison & Boolean operators
  5. IF & Else & Else If
  6. The switch operator
  7. What are methods?
  8. Methods structure
  9. Summary

NaughtySpirit Academy

Projects for this week

Math Wars

Spaceship Commander

Lecture Project

Homework Project

Conditionals

NaughtySpirit Academy

IF operator

boolean isLectureDay = true;

if(isLectureDay == true) {
    goToLecture();
    writeSomeCode();
}
if(CONDITION) {
    STATEMENT1;
    STATEMENT2;
        ...
    STATEMENTN;
}

NaughtySpirit Academy

Comparison operators

x > y: x is greater than y

x < y: x is less than y

 

int a = 10;
if(a = 10) {
// "=" Really !?
}
if("Test" == "Test") { // !?
// "Test".equals("Test")
}

x >= y: x is greater than or equal to x

x <= y: x is less than or equal to y

x == y: x equals y 

NaughtySpirit Academy

Boolean operators

&&: logical AND

||: logical OR 

boolean isProgrammerAtHome = true;
int workingHours = 3;
if(isProgrammerAtHome) {
    if(workingHours < 8) {
        // You are fired :(
    }
}
boolean isProgrammerAtHome = true;
int workingHours = 3;
if(isProgrammerAtHome && workingHours < 8) {
    // You are fired :(
}

NaughtySpirit Academy

IF & ELSE

boolean isProgrammerHome = true, 
    shouldFireProgrammer = false;

if(!isProgrammerHome) {
    System.out.println("WORK HARDER!");
} else {
    shouldFireProgrammer = true;
}
if(CONDITION) {
    STATEMENT1;
} else {
    STATEMENT2;
}

NaughtySpirit Academy

IF & ELSE IF

if (CONDITION) {
    STATEMENTS
} else if (CONDITION) {
    STATEMENTS
} else if (CONDITION) {
    STATEMENTS
} else {
    STATEMENTS
}
boolean isProgrammerAtHome = false;
int workingHours = 8;
if(isProgrammerAtHome) {
    // Fire
} else if(workingHours < 8) {
    // Fire
} else {
    // WORK HARDER!
}

NaughtySpirit Academy

SWITCH

int workingHours = 8;
// Default value is ...?
boolean shouldReceiveBonus; 
switch(workingHours) {
    case 8:
        shouldReceiveBonus = true;
        break;
    case 9:
        shouldReceiveBonus = true;
        break;
    default:
        shouldReceiveBonus = false;
}
int workingHours = 8;
boolean shouldReceiveBonus;
switch(workingHours) {
    case 8:
    case 9:
        shouldReceiveBonus = true;
        break;
    default:
        shouldReceiveBonus = false;
}
switch(CONDITION) {
    case CONDITION1:
        break;
    case CONDITIONN:
        break;
    default:
}
switch(1) {
    case 1:
        print("No break !?")
    case 2:
        print("I am leaving")
}
// Result: 
// No break !? 
// I am leaving

NaughtySpirit Academy

Task time

Questions?

NaughtySpirit Academy

Break (10 mins)

NaughtySpirit Academy

Methods (Functions)

  • A subprogram - a set of code
  • Must have return type
  • May or may not have input
  • May or may not return result
  • Can be called by name

When the method execution is finished the program returns to the area of the code from which it was called and continues on to the next line of code.

NaughtySpirit Academy

What is the function of a bread bakery?

NaughtySpirit Academy

Input?

Method signature

public static void NAME() {
    STATEMENTS;
}

NaughtySpirit Academy

Run example


private static void makeBread() {
    print("Your bread is ready, sir!");
}

public static void main (String[] args) {
    // Call method
    makeBread();
}

Parameters

public static void method(TYPE NAME) {
    STATEMENTS;
}

NaughtySpirit Academy

Run example


private static void makeBread(int flourAmount) {
    print("Your bread with " + flourAmount + 
        "kg of flour is ready, sir!");
}

public static void main (String[] args) {
    makeBread(5);
}

Multiple Parameters

public static void NAME(TYPE NAME, TYPE NAME) {
    STATEMENTS;
}

NaughtySpirit Academy

Run example


private static void makeBread(int flourAmount, int waterAmount) {
    print("Your bread with " + flourAmount + "kg of flour and " 
	+ waterAmount + "L of water is ready, sir!");
}
public static void main (String[] args) {
    makeBread(5, 2);
}

Return Values

public static TYPE NAME() {
    STATEMENTS
    return EXPRESSION;
}

void is the word for "no type"

void a = ""; // !?

NaughtySpirit Academy

Methods example


public static int multiply(int  a, int b) {
    return a * b;
}
 
public static int pow(int  number, int degree) {
    int result = 0;
    switch(degree) {
        case 2:
            result = multiply(number, number);
                break;
        case 3:
            result = multiply(multiply(number, number), 
                             number);
            break;
    }
    return result;
}
 
public static void main (String[] args) {
    print(pow(2, 3));
}

NaughtySpirit Academy

Run example

Methods Summary

  • They are a block of code

  • Programs are built of small methods
  • Methods can be reused and tested individually
  • Keeping methods small will make your life better
  • The caller of the method does not need to know how it works
  • This is called "abstraction"

NaughtySpirit Academy

Math Wars 2

Questions?

NaughtySpirit Academy

Summary

NaughtySpirit Academy

  • Conditional operators evaluate an expression to tell if it is true or false
  • Use if-else-elseif when you don't have many conditions
  • Use switch if you have more than 4 or 5 conditions
  • Use comparison operators to skip or shorten conditional ones
  • A method is a set of code
  • Methods may have return type and input params
  • Keep methods small and simple
  • Methods create a reusable code abstraction

Daily reminder test

http://goo.gl/forms/NBcpmUphBK

Thank you :)

Lecture 3 - Methods and Conditionals

By naughtyspirit

Source: Georgi Mirchev

Lecture 3 - Methods and Conditionals

  • 414

More from naughtyspirit