BAEL-2419: Added String Concatenation Unit Tests (#5898)

java-strings/src/test/java/com/baeldung/StringConcatenationUnitTest.java

@@ -0,0 +1,105 @@
+package com.baeldung;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.StringJoiner;
+import java.util.stream.Collectors;
+
+import static org.junit.Assert.assertEquals;
+
+public class StringConcatenationUnitTest {
+
+  @Test
+  public void givenMultipleStrings_whenConcatUsingStringBuilder_checkStringCorrect() {
+
+    StringBuilder stringBuilder = new StringBuilder(100);
+    stringBuilder.append("Baeldung");
+    stringBuilder.append(" is");
+    stringBuilder.append(" awesome");
+
+    assertEquals("Baeldung is awesome", stringBuilder.toString());
+
+  }
+
+  @Test
+  public void givenMultipleString_whenConcatUsingAdditionOperator_checkStringCorrect() {
+
+    String myString = "The " + "quick " + "brown " + "fox...";
+
+    assertEquals("The quick brown fox...", myString);
+  }
+
+
+  @Test
+  public void givenMultipleStrings_whenConcatUsingStringFormat_checkStringCorrect() {
+
+    String myString = String.format("%s %s %.2f %s %s, %s...", "I",
+            "ate",
+            2.5056302,
+            "blueberry",
+            "pies",
+            "oops");
+
+
+    assertEquals("I ate 2.51 blueberry pies, oops...", myString);
+  }
+
+  @Test
+  public void givenMultipleStrings_whenStringConcatUsed_checkStringCorrect() {
+
+    String myString = "Both".concat(" fickle")
+            .concat(" dwarves")
+            .concat(" jinx")
+            .concat(" my")
+            .concat(" pig")
+            .concat(" quiz");
+
+    assertEquals("Both fickle dwarves jinx my pig quiz", myString);
+
+
+  }
+
+  @Test
+  public void givenMultipleStrings_whenStringJoinUsed_checkStringCorrect() {
+
+    String[] strings = {"I'm", "running", "out", "of", "pangrams!"};
+
+    String myString = String.join(" ", strings);
+
+    assertEquals("I'm running out of pangrams!", myString);
+
+  }
+
+  @Test
+  public void givenMultipleStrings_whenStringJoinerUsed_checkStringCorrect() {
+
+    StringJoiner fruitJoiner = new StringJoiner(", ");
+    fruitJoiner.add("Apples");
+    fruitJoiner.add("Oranges");
+    fruitJoiner.add("Bananas");
+
+    assertEquals("Apples, Oranges, Bananas", fruitJoiner.toString());
+  }
+
+  @Test
+  public void givenMultipleStrings_whenArrayJoiner_checkStringCorrect() {
+
+    String[] myFavouriteLanguages = {"Java", "JavaScript", "Python"};
+
+    String toString = Arrays.toString(myFavouriteLanguages);
+
+    assertEquals("[Java, JavaScript, Python]", toString);
+  }
+
+  @Test
+  public void givenArrayListOfStrings_whenCollectorsJoin_checkStringCorrect() {
+
+    List<String> awesomeAnimals = Arrays.asList("Shark", "Panda", "Armadillo");
+
+    String animalString = awesomeAnimals.stream().collect(Collectors.joining(", "));
+
+    assertEquals("Shark, Panda, Armadillo", animalString);
+  }
+}