[BAEL-7170] Examples of colon character in Java (#15298)

core-java-modules/core-java-lang-operators-2/src/main/java/com/baeldung/colonexamples/ColonExamples.java

@@ -0,0 +1,178 @@
+package com.baeldung.colonexamples;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.Connection;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * Examples of the different ways Java uses the colon (:) character.
+ */
+public class ColonExamples {
+
+    private final static Logger LOG = LoggerFactory.getLogger(ColonExamples.class);
+
+    public void example1_enhancedForLoop() {
+
+        // Original style
+        for(int i = 0; i < 10; i++) {
+            // do something
+        }
+
+        // Using enhanced for loop
+        int[] numbers = new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9};
+        for(int i : numbers) {
+            // do something
+        }
+
+        // Using List instead of array
+        List<Integer> numbersList = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
+        for(Integer i : numbersList) {
+            // do something
+        }
+    }
+
+    public void example2_switchStatement(String animal) {
+
+        // Original style
+        if(animal.equals("cat")) {
+            System.out.println("meow");
+        }
+        else if(animal.equals("lion")) {
+            System.out.println("roar");
+        }
+        else if(animal.equals("dog") || animal.equals("seal")) {
+            System.out.println("bark");
+        }
+        else {
+            System.out.println("unknown");
+        }
+
+        // Using switch statement
+        switch(animal) {
+            case "cat":
+                System.out.println("meow");
+                break;
+            case "lion":
+                System.out.println("roar");
+                break;
+            case "dog":
+            case "seal":
+                System.out.println("bark");
+                break;
+            default:
+                System.out.println("unknown");
+        }
+    }
+
+    public void example3_labels() {
+
+        // For loops without labels
+        for(int i = 0; i < 10; i++) {
+            for (int j = 0; j < 10; j++) {
+                if (checkSomeCondition()) {
+                    break;
+                }
+            }
+        }
+
+        outterLoop: for(int i = 0; i < 10; i++) {
+            innerLoop: for (int j = 0; j < 10; j++) {
+                if (checkSomeCondition()) {
+                    break outterLoop;
+                }
+            }
+        }
+    }
+
+    public void example4_ternaryOperator() {
+
+        // Original way using if/else
+        int x;
+        if(checkSomeCondition()) {
+            x = 1;
+        }
+        else {
+            x = 2;
+        }
+
+        // Using ternary operator
+        x = checkSomeCondition() ? 1 : 2;
+
+        // Using with other statements
+        boolean remoteCallResult = callRemoteApi();
+        LOG.info(String.format(
+                "The result of the remote API call %s successful",
+                        remoteCallResult ? "was" : "was not"
+        ));
+    }
+
+    public void example5_methodReferences() {
+        // Original way without lambdas and method references
+        List<String> names = Arrays.asList("ross", "joey", "chandler");
+        List<String> upperCaseNames = new ArrayList<>();
+        for(String name : names) {
+            upperCaseNames.add(name.toUpperCase());
+        }
+
+        // Using method reference with stream map operation
+        List<String> petNames = Arrays.asList("ross", "joey", "chandler");
+        List<String> petUpperCaseNames = petNames
+            .stream()
+            .map(String::toUpperCase)
+            .collect(Collectors.toList());
+
+        // Method reference with stream filter
+        List<Animal> pets = Arrays.asList(new Cat(), new Dog(), new Parrot());
+        List<Animal> onlyDogs = pets
+            .stream()
+            .filter(Dog.class::isInstance)
+            .collect(Collectors.toList());
+
+        // Method reference with constructors
+        Set<Animal> onlyDogsSet = pets
+            .stream()
+            .filter(Dog.class::isInstance)
+            .collect(Collectors.toCollection(TreeSet::new));
+    }
+
+    public void example6_asserttion() {
+        // Original way without assertions
+        Connection conn = getConnection();
+        if(conn == null) {
+            throw new RuntimeException("Connection is null");
+        }
+
+        // Using assert keyword
+        assert getConnection() != null : "Connection is null";
+    }
+
+    private boolean checkSomeCondition() {
+        return new Random().nextBoolean();
+    }
+
+    private boolean callRemoteApi() {
+        return new Random().nextBoolean();
+    }
+
+    private Connection getConnection() {
+        return null;
+    }
+
+    private static interface Animal {
+
+    }
+    private static class Dog implements Animal {
+
+    }
+
+    private static class Cat implements Animal {
+
+    }
+
+    private static class Parrot implements Animal {
+
+    }
+}