Methods & Conditionals

What if...

By NaughtySpirit Academy

Quick reminder

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

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Weekly test time

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

Today's content

Projects
What are conditionals?
The If operator
Comparison & Boolean operators
IF & Else & Else If
The switch operator
What are methods?
Methods structure
Summary

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Projects for this week

Math Wars

Spaceship Commander

Lecture Project

Homework Project

Conditionals

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IF operator

boolean isLectureDay = true;

if(isLectureDay == true) {
    goToLecture();
    writeSomeCode();
}

if(CONDITION) {
    STATEMENT1;
    STATEMENT2;
        ...
    STATEMENTN;
}

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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

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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 :(
}

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IF & ELSE

boolean isProgrammerHome = true, 
    shouldFireProgrammer = false;

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

if(CONDITION) {
    STATEMENT1;
} else {
    STATEMENT2;
}

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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!
}

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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

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Task time

Questions?

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Break (10 mins)

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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.

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What is the function of a bread bakery?

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Input?

Method signature

public static void NAME() {
    STATEMENTS;
}

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R un 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;
}

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R un 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;
}

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R un 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 = ""; // !?

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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));
}

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R un example