FEAT StringUtils + tests

src/main/java/de/nclazz/commons/StringUtils.java

@@ -0,0 +1,78 @@
+package de.nclazz.commons;
+
+public abstract class StringUtils {
+
+    private StringUtils() { /* no-op */ }
+
+    /**
+     * Checks if a String is null or does not contain a character
+     * other than whitespace.
+     *
+     * @param s String to check
+     * @return {@code true} if String is empty
+     */
+    public static boolean isEmpty(String s) {
+        if(s == null) {
+            return true;
+        }
+        if(s.isEmpty()) {
+            return true;
+        }
+        for(int i = 0; i < s.length(); i++) {
+            if(!Character.isWhitespace(s.charAt(i))) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Capitalizes a String, meaning only the first letter becomes an
+     * upper case letter if not already.
+     * <p>i.e. {@code fooBar} -> {@code FooBar}</p>
+     * @param s String to capitalize
+     * @return capitalized String
+     * @see #decapitalize(String)
+     */
+    public static String capitalize(String s) {
+        if(s != null) {
+            s = s.substring(0, 1).toUpperCase() + s.substring(1);
+        }
+        return s;
+    }
+
+    /**
+     * Decapitalizes a String, meaning only the first letter becomes a
+     *lower case letter if not already.
+     * <p>i.e. {@code FooBar} -> {@code fooBar}</p>
+     * @param s String to decapitalize
+     * @return decapitalized String
+     * @see #capitalize(String)
+     */
+    public static String decapitalize(String s) {
+        if(s != null) {
+            s = s.substring(0, 1).toLowerCase() + s.substring(1);
+        }
+        return s;
+    }
+
+    public static String center(String s, int size) {
+        return center(s, size, ' ');
+    }
+
+    public static String center(String s, int size, char pad) {
+        if (s == null || size <= s.length())
+            return s;
+
+        StringBuilder sb = new StringBuilder(size);
+        for (int i = 0; i < (size - s.length()) / 2; i++) {
+            sb.append(pad);
+        }
+        sb.append(s);
+        while (sb.length() < size) {
+            sb.append(pad);
+        }
+        return sb.toString();
+    }
+
+}

src/test/java/de/nclazz/commons/StringUtilsTests.java

@@ -0,0 +1,79 @@
+package de.nclazz.commons;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class StringUtilsTests {
+
+    @Test
+    void testStringIsEmpty_Success() {
+        String[] testStrings = {
+                "",
+                null,
+                "      ",
+                "\n",
+                "\r",
+                "\n\r",
+                "\n    \r      "
+        };
+
+        for(String str : testStrings) {
+            assertTrue(StringUtils.isEmpty(str));
+        }
+    }
+
+    @Test
+    void testStringIsEmpty_Fails() {
+        String[] testStrings = {
+                "a",
+                "   aa   ",
+                "\na",
+                "\ra",
+                "\na\r",
+                "\n  a  \r      "
+        };
+
+        for(String str : testStrings) {
+            assertFalse(StringUtils.isEmpty(str));
+        }
+    }
+
+    @Test
+    void testStringCapitalize() {
+        String[][] testStrings = {
+                { "foobar", "Foobar" },
+                { "Foobar", "Foobar" },
+                { "FOOBAR", "FOOBAR" },
+                { "fOOBAR", "FOOBAR" },
+                { "1foobar", "1foobar" },
+                { "_foobar", "_foobar" },
+                { "?foobar", "?foobar" },
+                { "f?oobar", "F?oobar" },
+        };
+
+        for(String[] arr : testStrings) {
+            assertEquals(arr[1], StringUtils.capitalize(arr[0]));
+        }
+    }
+
+    @Test
+    void testStringDecapitalize() {
+        String[][] testStrings = {
+                { "foobar", "Foobar" },
+                { "foobar", "Foobar" },
+                { "fOOBAR", "FOOBAR" },
+                { "fOOBAR", "FOOBAR" },
+                { "1foobar", "1foobar" },
+                { "_foobar", "_foobar" },
+                { "?foobar", "?foobar" },
+                { "f?oobar", "F?oobar" },
+        };
+
+        for(String[] arr : testStrings) {
+            assertEquals(arr[0], StringUtils.decapitalize(arr[1]));
+        }
+    }
+
+}