Comparable VS Comparator: example

diff --git a/Allgemeines/ComparableVSComparator/src/de/comparable/example/Country.java b/Allgemeines/ComparableVSComparator/src/de/comparable/example/Country.java
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+++ b/Allgemeines/ComparableVSComparator/src/de/comparable/example/Country.java
@@ -0,0 +1,27 @@
+package de.comparable.example;
+
+
+public class Country implements Comparable<Country> {
+    private final int countryId;
+    private final String countryName;
+
+    public Country(final int countryId, final String countryName) {
+        this.countryId = countryId;
+        this.countryName = countryName;
+    }
+
+    @Override
+    public int compareTo(final Country country) {
+        return (this.countryId < country.countryId) ? -1
+                : (this.countryId > country.countryId) ? 1 : 0;
+    }
+
+    public int getCountryId() {
+        return this.countryId;
+    }
+
+    public String getCountryName() {
+        return this.countryName;
+    }
+
+}
\ No newline at end of file

diff --git a/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountryNoComparable.java b/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountryNoComparable.java
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+++ b/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountryNoComparable.java
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+package de.comparable.example;
+
+public class CountryNoComparable {
+    private final int countryId;
+    private final String countryName;
+
+    public CountryNoComparable(final int countryId, final String countryName) {
+        this.countryId = countryId;
+        this.countryName = countryName;
+    }
+
+    public int getCountryId() {
+        return this.countryId;
+    }
+
+    public String getCountryName() {
+        return this.countryName;
+    }
+}

diff --git a/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountrySortByIdComparator.java b/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountrySortByIdComparator.java
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+++ b/Allgemeines/ComparableVSComparator/src/de/comparable/example/CountrySortByIdComparator.java
@@ -0,0 +1,13 @@
+package de.comparable.example;
+
+import java.util.Comparator;
+
+public class CountrySortByIdComparator implements Comparator<Country> {
+
+    @Override
+    public int compare(final Country country1, final Country country2) {
+        return (country1.getCountryId() < country2.getCountryId()) ? -1
+                : (country1.getCountryId() > country2.getCountryId()) ? 1 : 0;
+    }
+
+}

diff --git a/Allgemeines/ComparableVSComparator/src/de/comparable/example/Example.java b/Allgemeines/ComparableVSComparator/src/de/comparable/example/Example.java
new file mode 100644 (file)
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+++ b/Allgemeines/ComparableVSComparator/src/de/comparable/example/Example.java
@@ -0,0 +1,117 @@
+package de.comparable.example;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * <p>
+ * Comparable: to be used by objects which want to be compared.
+ * </p>
+ * <p>
+ * Comparator: to be used by sort algorithms to change the sort comparison or
+ * when trying to sort objects which do not implement the Comparable interface
+ * because they did not intend to be compared.
+ * </p>
+ */
+public class Example {
+
+    public static void main(final String[] args) {
+        final Country indiaCountry = new Country(1, "India");
+        final Country chinaCountry = new Country(4, "China");
+        final Country nepalCountry = new Country(3, "Nepal");
+        final Country bhutanCountry = new Country(2, "Bhutan");
+        final Country bhutanCountryAgain = new Country(2, "Bhutan");
+
+        // 1. Using Comparable.
+        List<Country> listOfCountries = new ArrayList<Country>();
+        listOfCountries.add(indiaCountry);
+        listOfCountries.add(chinaCountry);
+        listOfCountries.add(nepalCountry);
+        listOfCountries.add(bhutanCountry);
+        listOfCountries.add(bhutanCountryAgain);
+
+        System.out.println("Before Sort  : ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country = listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "||"
+                    + "Country name: " + country.getCountryName());
+        }
+
+        Collections.sort(listOfCountries);
+
+        System.out.println("After Sort  : ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country = listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "|| "
+                    + "Country name: " + country.getCountryName());
+        }
+
+
+        // 2. Using Comparator (the same result)
+        listOfCountries = new ArrayList<Country>();
+        listOfCountries.add(indiaCountry);
+        listOfCountries.add(chinaCountry);
+        listOfCountries.add(nepalCountry);
+        listOfCountries.add(bhutanCountry);
+        listOfCountries.add(bhutanCountryAgain);
+
+        System.out.println("Before Sort by id : ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country=listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "||"
+                    + "Country name: " + country.getCountryName());
+        }
+
+        Collections.sort(listOfCountries,new CountrySortByIdComparator());
+
+        System.out.println("After Sort by id: ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country=listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "|| "
+                    + "Country name: " + country.getCountryName());
+        }
+
+
+        // 3. Using Comparator (with new sort)
+        // Country objects could not be designed to be compared, but by means of
+        // Comparator interface we could compare them even if the were not
+        // designed to be compared.
+        final CountryNoComparable indiaCountryNoComparable = new CountryNoComparable(1, "India");
+        final CountryNoComparable chinaCountryNoComparable = new CountryNoComparable(4, "China");
+        final CountryNoComparable nepalCountryNoComparable = new CountryNoComparable(3, "Nepal");
+        final CountryNoComparable bhutanCountryNoComparable = new CountryNoComparable(2, "Bhutan");
+        final CountryNoComparable bhutanCountryAgainNoComparable = new CountryNoComparable(2, "Bhutan");
+
+        final List<CountryNoComparable> listOfCountriesNoComparable = new ArrayList<CountryNoComparable>();
+        listOfCountriesNoComparable.add(indiaCountryNoComparable);
+        listOfCountriesNoComparable.add(chinaCountryNoComparable);
+        listOfCountriesNoComparable.add(nepalCountryNoComparable);
+        listOfCountriesNoComparable.add(bhutanCountryNoComparable);
+        listOfCountriesNoComparable.add(bhutanCountryAgainNoComparable);
+
+        System.out.println("Before Sort by name : ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country = listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "||"
+                    + "Country name: " + country.getCountryName());
+        }
+
+        Collections.sort(listOfCountriesNoComparable, new Comparator<CountryNoComparable>() {
+
+            @Override
+            public int compare(final CountryNoComparable o1, final CountryNoComparable o2) {
+                // We can compare even if CountryNoComparable was not designed for it :)
+                return o1.getCountryName().compareTo(o2.getCountryName());
+            }
+        });
+
+        System.out.println("After Sort by name: ");
+        for (int i = 0; i < listOfCountries.size(); i++) {
+            final Country country=listOfCountries.get(i);
+            System.out.println("Country Id: " + country.getCountryId() + "|| "
+                    + "Country name: " + country.getCountryName());
+        }
+    }
+}