fix: Reduce memory allocations and improve performance in JSONObject

Author: basil

subprojects/json-lib-core/src/main/java/org/kordamp/json/JSONObject.java

@@ -656,7 +656,7 @@ public static JSONObject fromJSONTokener(JSONTokener tokener, JsonConfig jsonCon
                 String key;
                 Object value;
 
-                if (tokener.matches("null.*")) {
+                if (tokener.startsWith("null")) {
                     fireObjectStartEvent(jsonConfig);
                     fireObjectEndEvent(jsonConfig);
                     return new JSONObject(true);

subprojects/json-lib-core/src/main/java/org/kordamp/json/util/JSONTokener.java

@@ -114,6 +114,10 @@ public boolean matches(String pattern) {
             .matches(str);
     }
 
+    public boolean startsWith(String prefix) {
+        return this.mySource.startsWith(prefix, this.myIndex);
+    }
+
     /**
      * Determine if the source string still contains characters that next() can
      * consume.

subprojects/json-lib-core/src/test/java/org/kordamp/json/util/TestJSONTokener.java

@@ -75,6 +75,20 @@ public void testNextChar() {
         }
     }
 
+    public void testStartsWith() {
+        assertFalse(new JSONTokener("").startsWith("null"));
+        assertFalse(new JSONTokener("n").startsWith("null"));
+        assertFalse(new JSONTokener("nu").startsWith("null"));
+        assertFalse(new JSONTokener("nul").startsWith("null"));
+        assertTrue(new JSONTokener("null").startsWith("null"));
+        assertTrue(new JSONTokener("nulll").startsWith("null"));
+        assertFalse(new JSONTokener("nn").startsWith("null"));
+        assertFalse(new JSONTokener("nnu").startsWith("null"));
+        assertFalse(new JSONTokener("nnul").startsWith("null"));
+        assertFalse(new JSONTokener("nnull").startsWith("null"));
+        assertFalse(new JSONTokener("nnulll").startsWith("null"));
+    }
+
     public void testReset() {
         JSONTokener tok = new JSONTokener("abc");
         tok.next();