[sb-null-or-empty] sb null or empty (#17404)

Author: sk1418

core-java-modules/core-java-string-apis-2/src/test/java/com/baeldung/stringbuildernullorempty/StringBuilderNullOrEmptyUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.stringbuildernullorempty;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+public class StringBuilderNullOrEmptyUnitTest {
+
+    private static final StringBuilder SB_NULL = null;
+    private static final StringBuilder SB_EMPTY = new StringBuilder();
+    private static final StringBuilder SB_EMPTY_STR = new StringBuilder("");
+    private static final StringBuilder SB_BLANK_STR = new StringBuilder("   ");
+    private static final StringBuilder SB_WITH_TEXT = new StringBuilder("I am a magic string");
+
+    public static boolean isNull(StringBuilder sb) {
+        return sb == null;
+    }
+
+    @Test
+    void whenCallingIsNull_thenCorrect() {
+        assertTrue(isNull(SB_NULL));
+
+        assertFalse(isNull(SB_EMPTY));
+        assertFalse(isNull(SB_EMPTY_STR));
+        assertFalse(isNull(SB_BLANK_STR));
+        assertFalse(isNull(SB_WITH_TEXT));
+    }
+
+    public static boolean isNullOrEmptyByStrEmpty(StringBuilder sb) {
+        return sb == null || sb.toString()
+            .isEmpty();
+    }
+
+    @Test
+    void whenCallingIsNullOrEmptyByStrEmpty_thenCorrect() {
+        assertTrue(isNullOrEmptyByStrEmpty(SB_NULL));
+        assertTrue(isNullOrEmptyByStrEmpty(SB_EMPTY));
+        assertTrue(isNullOrEmptyByStrEmpty(SB_EMPTY_STR));
+
+        assertFalse(isNullOrEmptyByStrEmpty(SB_BLANK_STR));
+        assertFalse(isNullOrEmptyByStrEmpty(SB_WITH_TEXT));
+    }
+
+    public static boolean isNullOrEmptyByLength(StringBuilder sb) {
+        return sb == null || sb.length() == 0;
+    }
+
+    @Test
+    void whenCallingIsNullOrEmptyByLength_thenCorrect() {
+        assertTrue(isNullOrEmptyByLength(SB_NULL));
+        assertTrue(isNullOrEmptyByLength(SB_EMPTY));
+        assertTrue(isNullOrEmptyByLength(SB_EMPTY_STR));
+
+        assertFalse(isNullOrEmptyByLength(SB_BLANK_STR));
+        assertFalse(isNullOrEmptyByLength(SB_WITH_TEXT));
+    }
+
+    public static boolean isNullOrEmpty(StringBuilder sb) {
+        return sb == null || sb.isEmpty();
+    }
+
+    @Test
+    void whenCallingIsNullOrEmpty_thenCorrect() {
+        assertTrue(isNullOrEmpty(SB_NULL));
+        assertTrue(isNullOrEmpty(SB_EMPTY));
+        assertTrue(isNullOrEmpty(SB_EMPTY_STR));
+
+        assertFalse(isNullOrEmpty(SB_BLANK_STR));
+        assertFalse(isNullOrEmpty(SB_WITH_TEXT));
+    }
+}