study utility classes

core-banking/src/com/example/banking/domain/Customer.java

@@ -48,6 +48,22 @@ public Optional<Account> getAccount(String iban) {
 		return Optional.empty();
 	}
 
+	public double getTotalBalance() {
+		var total = 0;
+		for (var account : accounts) {
+			total += account.getBalance();
+		}
+		return total;
+	}
+
+	public double getTotalBalance8() {
+		return accounts.stream()
+				       .parallel()
+				       //.mapToDouble(account -> account.getBalance())
+				       .mapToDouble(Account::getBalance)
+				       .sum(); // terminal method
+	}
+
 	public int getNumberOfAccounts() {
 		return accounts.size();
 	}

part1/src/com/example/exercises/Exercise2.java

@@ -1,7 +1,11 @@
 package com.example.exercises;
 
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
 import com.example.dao.CountryDao;
 import com.example.dao.InMemoryWorldDao;
+import com.example.domain.Country;
 
 /**
  * 
@@ -12,7 +16,16 @@ public class Exercise2 {
 	private static final CountryDao countryDao = InMemoryWorldDao.getInstance();
 
 	public static void main(String[] args) {
-		// Find the most populated city of each continent
+		var countries = countryDao.findAllCountries();
+		var stream = countries.stream();
+		if (countries.size()>1_000)
+			stream = stream.parallel();
+		var continents = stream
+		     .map(Country::getContinent)
+		     .distinct()
+		     .sorted((c1,c2)->c2.compareTo(c1))
+		     .collect(Collectors.toList()); // terminal
+		System.out.println(continents);
 	}
 
 }

part2/src/com/example/animals/domain/Cat.java

@@ -35,4 +35,9 @@ public void eat() {
 		System.out.println(String.format("%s is eating now...", name));
 	}
 
+	@Override
+	public String toString() {
+		return "Cat [name=" + name + ", legs=" + getLegs() + "]";
+	}
+
 }

part2/src/com/example/animals/domain/Fish.java

@@ -35,5 +35,10 @@ public void eat() {
 	public void walk() {
 		System.out.println(String.format("%s is swimming now...", name));
 	}
+
+	@Override
+	public String toString() {
+		return "Fish [name=" + name + ", legs= "+getLegs()+" ]";
+	}
 
 }

part2/src/com/example/animals/domain/Spider.java

@@ -14,4 +14,10 @@ public void eat() {
 		System.out.println("Spider is eating now...");
 	}
 
+	@Override
+	public String toString() {
+		return "Spider [legs=" + getLegs() + "]";
+	}
+
+
 }

part2/src/com/example/animals/exercises/Exercise3.java

@@ -1,6 +1,7 @@
 package com.example.animals.exercises;
 
 import java.util.Arrays;
+import java.util.Comparator;
 import java.util.List;
 
 import com.example.animals.domain.Animal;
@@ -18,6 +19,12 @@ public static void main(String[] args) {
 		// Find the animal with the highest number of legs
 		List<Animal> animals = Arrays.asList(new Cat(), new Spider(), new Cat("Tekir"), new Fish("Free Willy"),
 				new Spider(), new Fish("Jaws"));
+		animals.stream()
+		       .max(Comparator.comparing(Animal::getLegs))
+		       .ifPresent(System.out::println);
+		animals.stream()
+			   .min(Comparator.comparing(Animal::getLegs))
+			   .ifPresent(System.out::println);
 
 	}
 }

part2/src/com/example/animals/exercises/Exercise5.java

@@ -18,6 +18,7 @@ public static void main(String[] args) {
 		// Find the total number of legs
 		List<Animal> animals = Arrays.asList(new Cat(), new Spider(), new Cat("Tekir"), new Fish("Free Willy"),
 				new Spider(), new Fish("Jaws"));
-
+		var totalLegs = animals.stream().mapToLong(Animal::getLegs).sum();
+		System.out.println("Total legs: "+totalLegs);
 	}
 }

part2/src/com/example/animals/exercises/Exercise6.java

@@ -2,6 +2,7 @@
 
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import com.example.animals.domain.Animal;
 import com.example.animals.domain.Cat;
@@ -18,6 +19,12 @@ public static void main(String[] args) {
 		// Group the animals by their number of legs
 		List<Animal> animals = Arrays.asList(new Cat(), new Spider(), new Cat("Tekir"), new Fish("Free Willy"),
 				new Spider(), new Fish("Jaws"));
-
+		var animalsByLegs = 
+		    animals.stream()
+		           .collect(Collectors.groupingBy(Animal::getLegs));
+		animalsByLegs.forEach((legs,groupedAnimals)->{
+			System.out.println("Group: "+legs);
+			groupedAnimals.forEach(System.out::println);
+		});  
 	}
 }

study-utility-classes/.settings/org.eclipse.core.resources.prefs

@@ -0,0 +1,5 @@
+eclipse.preferences.version=1
+encoding//src/com/example/StudyCurrency.java=UTF-8
+encoding//src/com/example/StudyDateTimeFormatter.java=UTF-8
+encoding//src/com/example/StudyString.java=UTF-8
+encoding//src/com/example/StudyStringComparison.java=UTF-8

study-utility-classes/bin/messages_en_US.properties

@@ -0,0 +1 @@
+greeting=Hi {0}!

study-utility-classes/bin/messages_tr_TR.properties

@@ -0,0 +1 @@
+greeting=Merhaba, {0}!

study-utility-classes/src/com/example/StudyCurrency.java

@@ -0,0 +1,19 @@
+package com.example;
+
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.util.Locale;
+
+public class StudyCurrency {
+
+	public static void main(String[] args) {
+		var money = 12_345_678.9;
+		Locale locale = Locale.JAPAN; // new Locale("tr", "TR");
+		var df = (DecimalFormat) DecimalFormat.getCurrencyInstance(locale);
+		//var dfs = DecimalFormatSymbols.getInstance(locale);
+		//dfs.setCurrencySymbol("\u20BA");
+		//df.setDecimalFormatSymbols(dfs);
+		System.out.println(df.format(money));
+	}
+
+}

study-utility-classes/src/com/example/StudyDateTimeFormatter.java

@@ -0,0 +1,18 @@
+package com.example;
+
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
+import java.util.Locale;
+
+public class StudyDateTimeFormatter {
+
+	public static void main(String[] args) {
+		ZonedDateTime now = ZonedDateTime.now();
+		Locale tr = Locale.JAPAN; // new Locale("tr", "TR");
+		var dtf = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL, FormatStyle.FULL)
+				                   .withLocale(tr);
+		System.out.println(dtf.format(now));
+	}
+
+}

study-utility-classes/src/com/example/StudyDynamicString.java

@@ -0,0 +1,17 @@
+package com.example;
+
+public class StudyDynamicString {
+
+	public static void main(String[] args) {
+		// StringBuffer: TS, StringBuilder: NOT TS
+		var s = new StringBuffer(488891); 
+		var start = System.currentTimeMillis();
+		for (var i=0;i<2_000_000;++i) {
+			s.append(i); // dynamic string
+		}
+		var stop = System.currentTimeMillis();
+		System.out.println("s.length(): "+s.length()
+		 + ", duration: " + (stop-start) + " ms.");
+	}
+
+}

study-utility-classes/src/com/example/StudyI18N.java

@@ -0,0 +1,18 @@
+package com.example;
+
+import java.text.MessageFormat;
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+public class StudyI18N {
+
+	public static void main(String[] args) {
+		Locale tr = Locale.US; // new Locale("tr", "TR");
+		var bundle = ResourceBundle.getBundle("messages", tr);
+		String fullname= "Jack Bauer";
+		var formatter = new MessageFormat(bundle.getString("greeting"),tr);
+		System.out.println(formatter.format(new Object[] {fullname}));
+
+	}
+
+}

study-utility-classes/src/com/example/StudyString.java

@@ -0,0 +1,21 @@
+package com.example;
+
+import java.util.Locale;
+
+public class StudyString {
+
+	public static void main(String[] args) {
+		// String: immutable class -> object caching/pooling
+		String name = "jack"; 
+		System.out.println(name);
+		name = name.toUpperCase();
+		System.out.println(name);
+		var city = "izmir";
+		// Internationalization: i18n
+		var tr = new Locale("tr","TR"); 
+		System.out.println(city);
+		city = city.toUpperCase(tr); // supports i18n
+		System.out.println(city);
+	}
+
+}

study-utility-classes/src/com/example/StudyStringComparison.java

@@ -0,0 +1,38 @@
+package com.example;
+
+import java.text.Collator;
+import java.text.ParseException;
+import java.text.RuleBasedCollator;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+
+public class StudyStringComparison {
+
+	public static void main(String[] args) throws ParseException {
+		List<String> names = new ArrayList<>();
+		names.add("şule");
+		names.add("şima");
+		names.add("sema");
+		names.add("zehra");
+		names.add("ayşegül");
+		names.sort(String::compareTo);
+		System.out.println(names);
+		String name1 = "müller";
+		String name2 = "mueller";
+		System.out.println("name1.equals(name2): "+name1.equals(name2));
+		// Collation
+		String basicRules=  "< z < b < c < ç < d < e < f < g < ğ < h "+
+		        "< ı < i < j < k < l < m < n < o < ö < p "+
+		       "< r < s < ş < t < u < ü < v < y < a ";
+		String trExpension= "& ü ; ue & s ; ş" ;
+		final Collator collator= new RuleBasedCollator(basicRules + trExpension);
+		Collator.getInstance(new Locale("tr","TR"));
+		collator.setStrength(Collator.PRIMARY);		
+		System.out.println("name1.equals(name2): "+collator.equals(name1,name2));
+		System.out.println("sima==şima: "+collator.equals("sima","şima"));
+	    names.sort(collator::compare);
+	    System.out.println(names);
+	}
+
+}

study-utility-classes/src/messages_en_US.properties

@@ -0,0 +1 @@
+greeting=Hi {0}!

study-utility-classes/src/messages_tr_TR.properties

@@ -0,0 +1 @@
+greeting=Merhaba, {0}!