Java: Basic control flow

Introduction

 

Why Java

  • Cross platform between desktop environments
  • Strongly typed
  • Garbage collected
  • Compatibility with other languages

Products made with Java

  • Minecraft
  • Blu Ray players
  • Phonegap

Key structures

Overview of keywords

abstract   continue  for         new         switch
assert     default   goto        package     synchronized
boolean    do        if          private     this
break      double    implements  protected   throw
byte       else      import      public      throws
case       enum      instanceof  return      transient
catch      extends   int         short       try
char       final     interface   static      void
class      finally   long        strictfp    volatile
const      float     native      super       while

Variables

// Simple variables
boolean test       = true;
Color   color      = Color.RED;
String  hello      = "hello ";
String  world      = "world!";
Random  random     = new Random();
String  helloWorld = hello + world;
int     number     = 1;
double  decimal    = 0.5d;

// Generic ("type based types") variables
List<People> people  = new ArrayList<>();
Cage<Lion> lionCage = new Cage<>();

Variables quiz

? test = 0.5d;

? age = 22;

? list = new ArrayList<>();
double test = 0.5d;
int age = 22;
long age = 22;
List<String> list = new ArrayList<>();
ArrayList<String> list = new ArrayList<>();
List<?> list = new ArrayList<>();
ArrayList<?> list = new ArrayList<>();

Loops

// For loop
for (int i = 0; i < 30; i++) {

}

// while loop
boolean looping = true;
while (looping) {
    looping = false;
}


// Do while loop
boolean looping = true;
do {
    looping = false;
} while(looping);


// Foreach
String[] list = {"Hello", "World"};
for (String item : list) {

}

Condition statements

String red = "red";
String blue = "blue";


if (red.equals(blue)) {
    System.out.println("blue is red");
} else {
    System.out.println("blue is not red");
}

switch (red) {
    case "red":
        System.out.println("red is the color of roses");
        break;
    case "blue":
        System.out.println("blue is the color of the sky");
        break;
    case "green":
        System.out.println("green is the color of grass");
        break;
    case "yellow":
        System.out.println("yellow is the color of Mcdonald's");
        break;
}

User input

Scanner scanner = new Scanner(System.in);

while (scanner.hasNextLine()) {
    String line = scanner.nextLine();

    System.out.println(line.reverse());

}

Data storage constructions

Structures

Contents Unique Size changeable
Array values false false
List values false true
Set keys true true
Map keys,values true true

Array

String[] test = {"hi", "there"};

int[] numbers = {10, 20, 30};

int[] empty = new int[20];

empty[0] = 100;

System.out.println("Element at index 0: " + empty[0]);

List

List<String> list = new ArrayList<>();

List<String> list = new LinkedList<>();

list.add("hello world");

Set

Set<String> set = new HashSet<>();

set.add("hello world");
set.add("hello world");
set.add("hello");
set.add("world");

System.out.println(set);

Map

Map<String, Integer> map = new HashMap<>();

map.put("hello world", 1);
map.put("hello world", 2);
map.put("hello", 3);
map.put("world", 4);

System.out.println(map);

More?

Java tutorial

 

Java: Basic conrol flow

By Fernando van Loenhout

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Java: Basic conrol flow

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