diff --git a/src/main/java/org/json/InstanceCreator.java b/src/main/java/org/json/InstanceCreator.java
index 4836e23..c8ae05c 100644
--- a/src/main/java/org/json/InstanceCreator.java
+++ b/src/main/java/org/json/InstanceCreator.java
@@ -5,7 +5,7 @@ package org.json;
  *
  * @param <T> the type of instances created
  */
-public interface InstanceCreator<T> {
+interface InstanceCreator<T> {
 
   /**
    * Creates a new instance of type {@code T}.
diff --git a/src/main/java/org/json/JSONObject.java b/src/main/java/org/json/JSONObject.java
index fa16c3a..e0c0337 100644
--- a/src/main/java/org/json/JSONObject.java
+++ b/src/main/java/org/json/JSONObject.java
@@ -234,6 +234,16 @@ public class JSONObject {
         return (String) input;
       }
     });
+    classMapping.put(BigDecimal.class, new TypeConverter<BigDecimal>() {
+      public BigDecimal convert(Object input) {
+          return new BigDecimal((String) input);
+      }
+    });
+    classMapping.put(BigInteger.class, new TypeConverter<BigInteger>() {
+      public BigInteger convert(Object input) {
+          return new BigInteger((String) input);
+      }
+    });
 
     collectionMapping.put(List.class, new InstanceCreator<List>() {
       public List create() {
@@ -252,50 +262,6 @@ public class JSONObject {
     });
    }
 
-  /**
-   * Returns the current class-to-function mapping used for type conversions.
-   *
-   * @return a map of classes to functions that convert an {@code Object} to that class
-   */
-   public Map<Class<?>, TypeConverter<?>> getClassMapping() {
-     return classMapping;
-   }
-
-  /**
-   * Returns the current collection-to-supplier mapping used for instantiating collections.
-   *
-   * @return a map of collection interface types to suppliers of concrete implementations
-   */
-   public Map<Class<?>, InstanceCreator<?>> getCollectionMapping() {
-     return collectionMapping;
-   }
-
-  /**
-   * Adds or updates a type conversion function for a given class.
-   *
-   * <p>This allows users to customize how objects are converted into specific types
-   * during processing (e.g., JSON deserialization).
-   *
-   * @param clazz the target class for which the conversion function is to be set
-   * @param function a function that takes an {@code Object} and returns an instance of {@code clazz}
-   */
-   public void setClassMapping(Class<?> clazz, TypeConverter<?> function) {
-     classMapping.put(clazz, function);
-   }
-
-  /**
-   * Adds or updates a supplier function for instantiating a collection type.
-   *
-   * <p>This allows customization of which concrete implementation is used for
-   * interface types like {@code List}, {@code Set}, or {@code Map}.
-   *
-   * @param clazz the collection interface class (e.g., {@code List.class})
-   * @param function a supplier that creates a new instance of a concrete implementation
-   */
-   public void setCollectionMapping(Class<?> clazz, InstanceCreator<?> function) {
-     collectionMapping.put(clazz, function);
-   }
-
     /**
      * Construct a JSONObject from a subset of another JSONObject. An array of
      * strings is used to identify the keys that should be copied. Missing keys
diff --git a/src/main/java/org/json/TypeConverter.java b/src/main/java/org/json/TypeConverter.java
index dc07325..d5b4eaf 100644
--- a/src/main/java/org/json/TypeConverter.java
+++ b/src/main/java/org/json/TypeConverter.java
@@ -6,7 +6,7 @@ package org.json;
  *
  * @param <T> the target type to convert to
  */
-public interface TypeConverter<T> {
+interface TypeConverter<T> {
 
   /**
    * Converts the given input object to an instance of type {@code T}.
diff --git a/src/test/java/org/json/junit/JSONObjectTest.java b/src/test/java/org/json/junit/JSONObjectTest.java
index 7b81541..7ca6093 100644
--- a/src/test/java/org/json/junit/JSONObjectTest.java
+++ b/src/test/java/org/json/junit/JSONObjectTest.java
@@ -36,7 +36,6 @@ import org.json.JSONString;
 import org.json.JSONTokener;
 import org.json.ParserConfiguration;
 import org.json.XML;
-import org.json.TypeConverter;
 import org.json.junit.data.BrokenToString;
 import org.json.junit.data.ExceptionalBean;
 import org.json.junit.data.Fraction;
@@ -4121,17 +4120,13 @@ public class JSONObjectTest {
 
     @Test
     public void jsonObjectParseFromJson_1() {
-      JSONObject object = new JSONObject();
-      object.setClassMapping(java.time.LocalDateTime.class, new TypeConverter<java.time.LocalDateTime>() {
-        public java.time.LocalDateTime convert(Object input) {
-          return java.time.LocalDateTime.parse((String) input);
-        }
-      });
-      java.time.LocalDateTime localDateTime = java.time.LocalDateTime.now();
-      object.put("localDate", localDateTime.toString());
-      CustomClassA customClassA = object.fromJson(CustomClassA.class);
-      CustomClassA compareClassClassA = new CustomClassA(localDateTime);
-      assertEquals(customClassA, compareClassClassA);
+        JSONObject object = new JSONObject();
+
+        BigInteger largeInt = new BigInteger("123");
+        object.put("largeInt", largeInt.toString());
+        CustomClassA customClassA = object.fromJson(CustomClassA.class);
+        CustomClassA compareClassClassA = new CustomClassA(largeInt);
+        assertEquals(customClassA, compareClassClassA);
     }
 
     @Test
diff --git a/src/test/java/org/json/junit/data/CustomClassA.java b/src/test/java/org/json/junit/data/CustomClassA.java
index 275e9a5..08a99d3 100644
--- a/src/test/java/org/json/junit/data/CustomClassA.java
+++ b/src/test/java/org/json/junit/data/CustomClassA.java
@@ -1,17 +1,19 @@
 package org.json.junit.data;
 
+import java.math.BigInteger;
+
 public class CustomClassA {
-  public java.time.LocalDateTime localDate;
+  public BigInteger largeInt;
 
   public CustomClassA() {}
-  public CustomClassA(java.time.LocalDateTime localDate) {
-    this.localDate = localDate;
+  public CustomClassA(BigInteger largeInt) {
+    this.largeInt = largeInt;
   }
 
   @Override
   public boolean equals(Object o) {
     CustomClassA classA = (CustomClassA) o;
-    return this.localDate.equals(classA.localDate);
+    return this.largeInt.equals(classA.largeInt);
   }
 }