Java for advanced users

Java for Advanced Users
Combine Object-oriented Java with Functional coding
Marius Claassen,

Refine your programming skills, by using
the world’s most popular language to:
• Stay ahead of the competition
• Be the team leader
• Extend the language
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Marius Claassen,

About me
Marius Claassen, Java Developer and Teacher
I taught myself to program using Java. Having been a teacher for many
years, I am now working full-time as an independent software
instructor, making video tutorials. My passions are learning, teaching
and Java in equal measure. It is my mission to help others learn
programming in general and Java in particular.
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Benefits
• Implement advanced concepts
• Develop complex Java applications
• Devise Java solutions when given a
problem statement
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Major components
1. Introduction
2. Java class design
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture outline
• 30 Lectures
• 5 minutes
1. Video
2. PDF
3. Coding exercise
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Development tools
• JDK (SE 9)
http://www.oracle.com/technetwork/java/javase/downloads/jdk9-downloads-3848520.html
• IDE (IntelliJ IDEA)
https://www.jetbrains.com/idea/download/#section=windows
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Ideal student
Completed intermediate course
You want to specialize by:
• watching live coding
• doing coding exercises
• checking answers against solutions
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Marius Claassen,

Enrolment
• 30-day money back guarantee
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To access this course:
• https://www.udemy.com/course/1133522/manage/basics/
or
• mariusclaassen@gmail.com
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Marius Claassen,

TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 2: Interfaces example
Interfaces problem statement:
Implement an interface, ‘Startable’ to print
the strings, ‘Tractor started’ and
‘Dishwasher stopped’
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Lecture 2: Interfaces example
module com.advancedjava {
// requires module
exports com.advancedjava; // package
}
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package com.advancedjava;
public class Lecture2 {
public static void main(String[] args) {
Tractor tractor = new Tractor();
tractor.start();
System.out.print(“, ”);
Startable dishwasher = new Dishwasher();
dishwasher.stop(); } }
// Tractor started, Dishwasher stopped
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public interface Startable {
public void start();
public void stop();
}
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public class Tractor implements Startable {
@Override public void start() {
System.out.print(“Tractor started”); }
@Override public void stop() {
System.out.print(“Tractor stopped”); }
}
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public class Dishwasher implements Startable {
@Override public void start() {
System.out.print(“Dishwasher started”); }
@Override public void stop() {
System.out.print(“Dishwasher stopped”); }
}
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Lecture 2: Interfaces exercise
Implement an interface, ‘Openable’ to print
the strings, ‘Cashregister opened’ and ‘Utility
account closed’
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Lecture 3: Interfaces solution
// requires module
}
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Cashregister cashregister = new Cashregister();
cashregister.open();
System.out.print(“, ”);
Openable utilityAccount = new UtilityAccount();
utilityAccount.close(); } }
// Cashregister opened, Utility account closed
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public interface Openable {
public void open();
public void close();
}
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public class Cashregister implements Openable {
@Override public void open() {
System.out.print(“Cashregister opened”); }
@Override public void close() {
System.out.print(“Cashregister closed”); }
}
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public class UtilityAccount implements Openable {
@Override public void open() {
System.out.print(“Utility account opened”); }
@Override public void close() {
System.out.print(“Utility account closed”); }
}
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Lecture 4: Abstract class example
Abstract classes problem statement:
Implement an abstract class, ‘Vehicle’ to
print, ‘Car licensed’ and ‘Truck licensed’
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Lecture 4: Abstract class example
// requires module
}
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Car car = new Car();
car.licensing(“Car”);
Truck truck = new Truck();
truck.licensing(“Truck”); } }
// Car licensed, Truck licensed
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public abstract class Vehicle {
public abstract void licensing(String type);
}
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public class Car extends Vehicle {
@Override public void licensing(String type) {
System.out.print(type + “ licensed, ”);
}
}
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public class Truck extends Vehicle {
@Override public void licensing(String type) {
System.out.println(type + “ licensed”);
}
}
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Lecture 4: Abstract class exercise
Implement an abstract class, ‘Shape’ to print,
‘Circle diameter 10 metres’ and ‘Rectangle
size 15 square metres’
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Lecture 5: Abstract class solution
// requires module
}
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Circle circle = new Circle();
circle.resize(10);
Rectangle rectangle = new Rectangle();
rectangle.resize(15); } }
// Circle diameter 10 metres, Rectangle size 15 square metres
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public abstract class Shape {
public abstract void resize(int value);
}
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public class Circle extends Shape {
@Override public void resize(int diameter) {
System.out.println(“Circle diameter ”+diameter+“ metres”);
}
}
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public class Rectangle extends Shape {
@Override public void resize(int size) {
System.out.println(“Rectangle size ”+size+“ square
metres”);
}
}
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 6: Generics example
Generics problem statement:
Implement generics to print the first 3
Hebrew letters as Integer, String pairs.
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Lecture 6: Generics example
// requires module
}
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Map<Integer, String> firstLetters = Map.of(1, “Alef”, “ ”,
“Bet”, 3, “Gimmel”);
firstLetters.forEach( (k,v) -> System.out.println(k+ “ ” +v) );
} }
// 1 Alef 2 Bet 3 Gimmel
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Lecture 6: Generics exercise
Implement generics to print the world’s
largest 3 cities as String, Integer pairs.
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Map<String, Integer> largestCities = Map.of(“Shanghai”,
“24256800 ”, “Beijing”, 21516000, “Delhi”, 16787941);
firstLetters.forEach( (k,v) -> System.out.println(k+ “ ” +v) );
} }
// Shanghai 24356800 Beijing 21516000 Delhi 16787941
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Lecture 8: Collections 1 example
Collections Part 1 problem statement:
Implement the ‘List’ collection and the ‘skip()’
to print a subset of numbers.
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// requires module
}
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package com.advancedjava; import java.util.List;
List<Integer> ints = List.of(14, 15, 16, 17, 18, 18, 19, 20);
ints.stream().skip(3).forEach(i->System.out.print(i + “ ”) );
} }
// 17 18 18 19 20
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Lecture 8: Collections 1 exercise
Implement the ‘List’ collection and the ‘limit()’
to print a subset of words.
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Lecture 9: Collections 1 solution
// requires module
}
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package com.advancedjava; import java.util.List;
List<String> words = List.of(“Java”, ”is”, “number”, ”1”);
words.stream().limit(2).forEach(w->System.out.print(w+“ ”));
} }
// Java is
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Collections Part 2 problem statement:
Implement the ‘Set’ collection to print all the
words in a set.
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// requires module
}
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package com.advancedjava; import java.util.Set;
Set<String> metals=Set.of(“gold”, “diamonds”, “platinum”);
metals.stream().forEach(m ->System.out.print(m+“ ”));
} }
// gold diamonds platinum
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Lecture 10: Collections 2 exercise
Implement the ‘Set’ collection to print all the
fractional values in a set.
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// requires module
}
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Set<Double> values = List.of(31.5, 32.9, 33.7);
values.stream().forEach(v->System.out.print(v+“ ”));
} }
// 32.9 33.7 31.5
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Lecture 12: Sorting example
Sorting problem statement:
Implement the ‘Set’ collection to print
characters in their natural order.
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// requires module
}
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Set<Character> chars=Set.of( ‘%’, ‘#’, ‘&’, ‘$’, ‘!’, ‘ " ’);
chars.stream().sorted().forEach(c->System.out.print(c+“ ”));
} }
// ! " # $ % &
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Lecture 12: Sorting exercise
Implement the ‘List’ collection to print
weekdays in their natural order.
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Lecture 13: Sorting solution
// requires module
}
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Lecture 13: Sorting solution
package com.advancedjava; import java.time.DayOfWeek;
import java.util.List;
List<DayOfWeek> days = List.of(DayOfWeek.WEDNESDAY,
DayOfWeek.SATURDAY , DayOfWeek.MONDAY );
days.stream().sorted().forEach(d->System.out.print(d+“ ”));
} }
// MONDAY WEDNESDAY SATURDAY
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Lecture 14: Searching example
Searching problem statement:
Implement a ‘List’ and the ‘Optional’ class to
find the first integer divisible by 3.
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// requires module
}
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package com.advancedjava; import java.util.List; import
java.util.Optional;
List<Integer> integers = List.of(85, 86, 87, 88, 89, 90);
Optional<Integer>firstDivisibleBy3 = integers.stream()
.filter(i -> i % 3 == 0).findFirst();
System.out .println(firstDivisibleBy3));
} } // Optional [87]
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Lecture 14: Searching exercise
Implement a ‘List’ and the ‘Optional’ class to
find the first square divisible by 5.
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Lecture 15: Searching solution
// requires module
}
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Lecture 15: Searching solution
package com.advancedjava; import java.util.List; import
java.util.Optional;
List<Integer> integers = List.of(3, 5, 7, 9, 11);
Optional<Integer>firstSquareDivBy5 = integers.stream()
.map(i -> i * i).filter(i -> i % 5 == 0).findFirst();
System.out .println(firstSquareDivBy5));
} } // Optional [25]
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 16: String example
String processing problem statement:
Implement a ‘List<String>’ to return a stream
of unique letters.
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// requires module
}
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import java.util.List; import java.util.stream.Collectors; import
java.util.stream.Stream;
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List<String> words = List.of(“Java”, “the”, “legend”);
List<String> uniqueLetters = words.stream()
.flatMap(w -> Stream.of (w.split(“”)).distinct() )
.collect(Collectors.toList());
uniqueLetters.forEach(u->System.out .print(u+“ ”)); } }
// J a v t h e l g n d
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Lecture 16: String exercise
Implement a ‘List<String>’ to sort words
according to their length.
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Lecture 16: String exercise
Implement a ‘List<String>’ to sort words
according to their length.
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Lecture 17: String solution
// requires module
}
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import java.util.Comparator; import java.util.List; import
java.util.Collectors; import java.util.stream.Stream;
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List<String> words = List.of(“Java”, “the”, “legend”);
List<String> sortedWords = words.stream()
.flatMap(w -> Stream.of (w.split(“ ”))
.sorted(Comparator.comparingInt(String::length)) )
sortedWords.forEach(w->System.out .print(w+“ ”)); } }
// the Java legend
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Lecture 18: Regular expr example
Regular expression problem statement:
Implement the regular expression ‘be’ to
operate on a list of words. Create a single
string, replacing the regular expressions with
a question mark.
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// requires module
}
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final String REG_EXPR = “be’’;
List<String> words = List.of(“To be, or not to be: That is the
question:”);
String regExpr = words.stream().flatMap(w ->Stream.of
(w.split(REG_EXPR ))) .collect(Collectors.joining(“?”));
System.out .print(regExpr); } }
// To ?, or not to ?: that is the question:
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Lecture 18: Regular expr exercise
Implement the regular expression ‘re’ to
operate on a list of words. Create a single
string, replacing the regular expressions with
a hyphen.
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Lecture 19: Regular expr solution
// requires module
}
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final String REG_EXPR = “re’’;
List<String> words = List.of(“There are more things in
heaven and earth, Horatio,”);
String regExpr = words.stream().flatMap(w -> Stream.of
(w.split(REG_EXPR ))) .collect(Collectors.joining(“-”));
System.out .print(regExpr); } }
// The- a- mo- things in heaven and earth, Horatio,
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 20: Recursion example
Recursion problem statement:
Implement a recursive method to calculate
the factorial of 5.
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// requires module
}
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long n = 5;
System.out .print(“Factorial of ” + n + “: ” + factorial(n));
}
// Factorial of 5: 120
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public static long factorial(long value) {
return factHelper(1, value); }
public static long factHelper(long acc, long num) {
return num == 1 ? acc : factHelper(acc * num, num - 1); }
}
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Lecture 20: Recursion exercise
Implement a recursive method to calculate
the factorial of 9.
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Lecture 21: Recursion solution
// requires module
}
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Lecture 21: Recursion solution
long n = 9;
System.out .print(“Factorial of ” + n + “: ” + factorial(n));
}
// Factorial of 9: 362880
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public static long factorial(long value) {
return factHelper(1, value); }
public static long factHelper(long acc, long num) {
return num == 1 ? acc : factHelper(acc * num, num - 1); }
}
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 22: Input example
Input problem statement:
Implement a ‘BufferedReader’ to read input
from a text file, and create a list of those
words.
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// requires module
}
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import java.io.BufferedReader; import java.io.IOException;
import java.nio.file.Files; import java.nio.file.Paths; import
java.util.List; import java.util.stream.Collectors;
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public static void main(String[] args) throws IOException {
try (BufferedReader reader = Files.newBufferedReader (
Paths.get(“InputL22.txt”))) {
List<String> words = reader.lines()
words.stream(forEach(System.out::println) );
}
} }
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InputL22.txt
“Love all, trust a few,
Do wrong to none: be able for thine enemy
Rather in power than use, and keep thy friend
Under thy own life’s key: be cheque’d for silence,
But never tax’d for speech.”
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// “Love all, trust a few,
// Do wrong to none: be able for thine enemy
// Rather in power than use, and keep thy friend
// Under thy own life’s key: be cheque’d for silence,
// But never tax’d for speech.”
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Lecture 22: Input exercise
Implement a ‘BufferedReader’ to read input
from a text file, and create a list of those
words.
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Lecture 23: Input solution
// requires module
}
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Lecture 23: Input solution
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words.stream(forEach(System.out::println) );
}
} }
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InputL23.txt
“Young men’s love then lies
Not truly in their hearts, but in their eyes.”
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// “Young men’s love then lies
// Not truly in their hearts, but in their eyes.”
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Lecture 24: Output example
Output problem statement:
Implement a ‘BufferedWriter’ for writing to a
text file.
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// requires module
}
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import java.io.BufferedWriter; import java.io.IOException;
import java.nio.file.Files; import java.nio.file.Paths;
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try (BufferedWriter writer = Files.newBufferedWriter (
Paths.get(“OutputL24.txt”))) {
writer.write(“n“This above all: to thine own self be true,n”+
“And it must follow, as the night the day, n”+
“Thou canst not then be false to any man.” ”);
} } }
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// “This above all: to thine own self be true,
// And it must follow, as the night the day,
// Thou canst not then be false to any man.”
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Lecture 24: Output exercise
Implement a ‘BufferedWriter’ for writing to a
text file.
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Lecture 25: Output solution
// requires module
}
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Lecture 25: Output solution
import java.io.BufferedWriter; import java.io.IOException;
import java.nio.file.Files; import java.nio.file.Paths;
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try (BufferedWriter writer = Files.newBufferedWriter (
Paths.get(“OutputL25.txt”))) {
writer.write(“n“Cowards die many times before their
deaths;n”+
“The valiant never taste of death but once” ”);
}
} }114
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// “Cowards die many times before their deaths;
// The valiant never taste of death but once”
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 26: Exceptions example
Exceptions problem statement:
Implement ‘try with resources’ to read from
and handle a ‘NoSuchFileException’.
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// requires module
}
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words.forEach(System.out::println);
}
} }
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// java.nio.file.NoSuchFileException
// Java is the number 1 development platform
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Lecture 26: Exceptions exercise
Implement ‘try with resources’ to read from
and handle a ‘NoSuchFileException’.
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Lecture 27: Exceptions solution
// requires module
}
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Lecture 27: Exceptions solution
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Paths.get(“Input27.txt”))) {
words.forEach(System.out::println);
}
} }
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// java.nio.file.NoSuchFileException
// There are 21 billion cloud connected virtual machines
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Lecture 28: Assertions example
Assertions problem statement:
Implement an ‘assertion’ statement to test for
equality where a list contains only even-
length words converted to capital letters.
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requires junit; // module
}
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import org.junit.Assert; import org.junit.Test;
import java.util.List; import java.util.stream.Collectors;
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@Test public void evenLengthCapitalWords() {
List<String> input = List.of(“Java”, “the” , “number1”,
“language”);
List<String> result = input.stream().filter(w -> w.length()
% 2 == 0).map(String::toUpperCase)
Assert.assertEquals(List.of(“JAVA”, “LANGUAGE”),result);
} } // [1 test passed]
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Lecture 28: Assertions exercise
Implement an ‘assertion’ to test for equality
of the longest line in a file.
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Lecture 29: Assertions solution
requires junit; // module
}
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Lecture 29: Assertions solution
import org.junit.After; import org.junit.Assert; import
org.junit.Before; import org.junit.Test;
java.util.Comparator;
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private BufferedReader = reader;
@Before public void setUpReader() throws IOException {
reader = Files.newBufferedReader (Paths.get(“L29.txt”)); }
@After public void closeReader() throws IOException {
reader.close(); }
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@Test public void findLongestLine() throws IOException {
String longest = reader.lines().max(Comparator
.comparingInt(String::length)).orElse(“ ”);
Assert.assertEquals(“the most popular programming
language in use, particularly for client-server web
applications,”, longest);
}
}
// [1 test passed]
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L29.txt
Java is a computer programming language that is concurrent, class-based, object-oriented
and specifically designed to have as few implementation dependencies as possible.
It is intended to let application developers "write once, run anywhere" (WORA),
meaning that code that runs on one platform does not need to be recompiled to run on another.
Java applications are typically compiled to bytecode (class file) that can run on any
Java virtual machine (JVM) regardless of computer architecture. Java is, as of 2017,
the most popular programming language in use, particularly for client-server web applications,
with a reported 12 million developers. Java was originally developed by James Gosling at
Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995
as a core component of Sun Microsystems' Java platform. The language derives much
of its syntax from C and C++, but it has fewer low-level facilities than either of them.
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TOPICS
1. Introduction
3. Collections
4. Strings
5. Recursion
6. Input / Output
7. Error handling
8. Conclusion
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Lecture 30: Final remarks
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To access this course:
• https://www.udemy.com/course/1133522/manage/basics/
or
• mariusclaassen@gmail.com
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Marius Claassen,

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