[strToChar] Convert String to char in Java (#12893)

core-java-modules/core-java-string-operations-5/src/test/java/com/baeldung/strtochar/ConvertStringToCharUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.strtochar;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ConvertStringToCharUnitTest {
+    private static final String STRING_b = "b";
+    private static final String STRING_Baeldung = "Baeldung";
+
+    @Test
+    void givenStringWithSingleChar_whenCallingCharAt_thenGetExpectedResult() {
+        assertEquals('b', STRING_b.charAt(0));
+        assertEquals('l', STRING_Baeldung.charAt(3));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> "".charAt(0));
+    }
+
+    @Test
+    void givenStringWithMultipleChars_whenCallingCharAt_thenGetExpectedResult() {
+        assertArrayEquals(new char[] { 'B', 'a', 'e', 'l', 'd', 'u', 'n', 'g' }, STRING_Baeldung.toCharArray());
+        assertArrayEquals(new char[] {}, "".toCharArray());
+    }
+
+    @Test
+    void givenStringWithMultipleChars_whenCallingGetChars_thenGetExpectedResult() {
+        char[] aeld = new char[4];
+        STRING_Baeldung.getChars(1, 5, aeld, 0);
+        assertArrayEquals(new char[] { 'a', 'e', 'l', 'd' }, aeld);
+
+        char[] anotherArray = new char[] { '#', '#', '#', '#', '#', '#' };
+        STRING_Baeldung.getChars(1, 5, anotherArray, 1);
+        assertArrayEquals(new char[] { '#', 'a', 'e', 'l', 'd', '#' }, anotherArray);
+    }
+}