public class EqualsExample {
    public static void main(String[] args) {
        String s1 = "Hello"; // string literal
        String s2 = new String("Hello"); // string class
        System.out.println(s1 == s2); // false, as its comparing the addresses of s1 and s2
        System.out.println(s1.equals(s2)); // true, compares the values at the addresses
        //                    ^ do this
    }
}

public class MagicNumbers {
    public void doSomething() {
        if (files.size() == 5) {} // what does 5 mean here?
    }
}

public class MagicNumbers {
    private final static int MAX_FILES = 5; 
    // declare constant with good name ^
    public void doSomething() {
        if (files.size() == MagicNumbers.MAX_FILES) {};
                                         // ^ use constant here
    }
}

public abstract class Shape {
    public abstract String getType();
}

public class Rectangle extends Shape {
    public void doSomething(List<Shape> shapes) {
        for (Shape s : shapes) {
            if (s.getClass().equals(Rectangle.class)) { 	// v1: kinda ok
                // do something only on exactly the Rectangle class
            }
            if (s.getType().equals("Rectangle")) { 		    // v2: very bad
               // do something on all rectangles
            }
            if (s instanceof Rectangle) { 					// v3: best choice here
                // do something on all rectangles
            }
        }
    }
}

public class Square extends Rectangle { ... }

public class TrainingSystem {
    public List<Trainer> trainers;
    /**
     * Try to booking training for an employee, given their availability.
     *
     * @param employee
     * @param availability
     * @return The date of their seminar if booking was successful, null there
     * are no empty slots in seminars on the day they are available.
     */
    public LocalDate bookTraining(String employee, List<LocalDate> availability) {
        for (Trainer trainer : trainers) {
            LocalDate booked = trainer.book(employee, availability);
            if (booked != null)
                return booked;
        }
        return null;
    }
}

/**
 * A trainer that runs in person seminars.
 */
public class Trainer {
    private String name;
    private String room;
    private List<Seminar> seminars;

    public List<Seminar> getSeminars() {
        return seminars;
    }

    /**
     * Try to book one of this trainer's seminars.
     * @param employee
     * @param availability
     * @return The date of the seminar if booking was successful, null if the
     * trainer has no free slots in seminars on the available days.
     */
    public LocalDate book(String employee, List<LocalDate> availability) {
        for (Seminar seminar : seminars) {
            LocalDate booked = seminar.book(employee, availability);
            if (booked != null)
                return booked;
        }
        return null;
    }
}

/**
 * An online seminar is a video that can be viewed at any time by employees. A
 * record is kept of which employees have watched the seminar.
 */
public class OnlineSeminar extends Seminar {
    private String videoURL;
    private List<String> watched;
}

public class OptionalExample {
    public static void main(String[] args) {
        List<String> strings = new ArrayList<String>(Arrays.asList(new String[] { "1", "2", "3", "4", "5" }));
        Optional<String> res = strings.stream().filter(x -> x.equals("1")).findAny();

        if (res.isPresent()) {
            System.out.println(res.get());
        } else {
            // It doesn't exist
            // Handle error?
        }
    }
}

package stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class App {
    public static void main(String[] args) {
    	// Exercise 1
        List<String> strings = new ArrayList<String>(Arrays.asList(new String[] { "1", "2", "3", "4", "5" }));
        for (String string : strings) {
            System.out.println(string);
        }
	
    	// Exercise 2
        List<Integer> ints = new ArrayList<Integer>();
        for (String string : strings) {
            ints.add(Integer.parseInt(string));
        }
        System.out.println(ints);
    }

}

package stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class App {
    public static void main(String[] args) {
    	// Exercise 1 Solution
        List<String> strings = new ArrayList<String>(Arrays.asList(new String[] { "1", "2", "3", "4", "5" }));
        strings.stream().forEach(x -> System.out.println(x));
        strings.stream().forEach(x -> {
            System.out.println(x);
        });
		
        // Exercise 2 Solution
        List<Integer> parsedStrings = strings.stream().map(x -> Integer.parseInt(x)).collect(Collectors.toList());
        strings2.stream().map(x -> Integer.parseInt(x)).forEach(x -> System.out.println(x));
    }
}

package stream;

public abstract class GenericSatellite {
    private double linearSpeed; // in KM/minute
    private String name; // name of satellite

    public GenericSatellite(double linearSpeed, String name) {
        this.linearSpeed = linearSpeed;
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    public double getLinearSpeed() {
        return this.linearSpeed;
    }
}

package stream;

public class FastSatellite extends GenericSatellite {
    private static final double speed = 100.0;

    public FastSatellite(String name) {
        super(speed, name);
    }
}

package stream;

public class SlowSatellite extends GenericSatellite {
    private static final double speed = 50.0;

    public SlowSatellite(String name) {
        super(SlowSatellite.speed, name);
    }
}

package stream;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class Controller {
    private List<GenericSatellite> satellites = new ArrayList<>();

    public void addSatellite(GenericSatellite satelliteToAdd) {
        this.satellites.add(satelliteToAdd);
    }

    public List<GenericSatellite> getSatelliteList() {
        return this.satellites;
    }
    
    public static void main(String[] args) { ... }
}

public static void main(String[] args) {
    Controller c = new Controller();
    c.addSatellite(new FastSatellite("Fast Satellite 1"));
    c.addSatellite(new FastSatellite("Fast Satellite 2"));
    c.addSatellite(new SlowSatellite("Slow Satellite 1"));

    List<GenericSatellite> allSatellites = c.getSatelliteList();

    // What if I just want FastSatellites only?
    // Method 1, normal for-in/for-each
    List<GenericSatellite> fast1 = new ArrayList<>();
    for (GenericSatellite x : allSatellites) {
        if (x instanceof FastSatellite) {
            fast1.add(x);
        }
    }

    // Method 2, streams
    List<GenericSatellite> fast2 = allSatellites
    	.stream()
        .filter(x -> x instanceof FastSatellite)
        .collect(Collectors.toList());

    // Same, but I typecast at the same time
    List<FastSatellite> fast3 = allSatellites
    	.stream()
        .filter(x -> x instanceof FastSatellite)
        .map(x -> (FastSatellite) x)
        .collect(Collectors.toList());
}

public static void main(String[] args) {
    Controller c = new Controller();
    List<GenericSatellite> allSatellites = c.getSatelliteList();

    // What if im trying to look for a satellite with name == "Fast Satellite 2"?
    // Method 1, normal for-in/for-each
    GenericSatellite g1 = null;
    for (GenericSatellite x : allSatellites) {
        if (x.getName().equals("Fast Satellite 2")) {
            g1 = x;
            break;
        }
    }

    // Method 2, streams
    Optional<GenericSatellite> g2 = allSatellites
      .stream()
      .filter(x -> x.getName().equals("Fast Satellite 2"))
      .findAny();
}