# Quick Java Tutorial

## Overview

On this page we will cover

* [Variables](#variables)
* [Conditionals](#conditionals)
* [Loops](#loops)
* [Methods](#class-methods)
* [Classes](#classes)
* [Objects](#using-objects)

## Variables

```
/* Syntax: Type variableName = VALUE; */

int wholeNumber = 93;
double numberWithDigits = 46.85;

String text = "words and stuff";

boolean isValid = true;
boolean isNegative = -3 < 0;

MyObject obj = new MyObject();
```

## Conditionals

```
if (boolean1) {
    // if boolean1 is true
} else if (boolean2) {
    // if boolean1 is false but boolean2 is true
} else {
    // if boolean1 and boolean2 were both false
}
```

## Loops

```
while (isLoopActive) {
    // keep doing something
}
// isLoopActive became false
```

```
for (int i = 0; i < 5; i++) { // start with i=0, increment i each time, continue while i < 5
    // do something 5 times
}
```

## Class Methods

```
/* Syntax: keywords returnType methodName(ParameterType parameterName, ...) { */

public static final double divide(int dividend, double divisor) {
    double quotient = dividend / divisor;
    return quotient;
}

private void moveForward(double inches) {
    // code to move forward [inches] inches
    // don't need to return, as returnType is 'void'
}

public abstract void overrideMeLater;
```

Keywords:

| Access Modifier keyword | Description                                               |
| ----------------------- | --------------------------------------------------------- |
| public                  | Method is accessible by any class                         |
| private                 | Method is accessible by the same class                    |
| protected               | Method is accessible by the same class and any subclasses |
| \[leave blank]          | Method is accessible only by the class's object           |

| Non-Access Modifier keyword | Description                                                              |
| --------------------------- | ------------------------------------------------------------------------ |
| static                      | Method belongs to class \[Class.call()], not the object \[object.call()] |
| abstract                    | Method must be overridden and does not have a body                       |
| final                       | Method cannot be overridden                                              |

## Classes

```
public class ClassName {
    // class variables here
    String name;
    
    // constructor
    public ClassName() {
        this("default name");
    }
    public ClassName(String name) {
        this.name = name;
    }
    
    // class methods here
    public String getName() {
        return name;
    }
}
```

## Using Objects

```
// Creating objects
MyObject objName1 = new MyObject();
MyObject objName2 = new MyObject("Second try");

// Calling methods
MyObject.staticMethod();
objName1.method();
objName2.method();

// Using return values
String output = objName1.toString() + " | " + objName2.toString();


// Note: objects are just unique instances of a class; 
//       you can have multiple of the same class
```


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