Summary
-------

Add the method `Class.forPrimitiveName(String)` to map from the name of a primitive type (`int`, `long`, etc.) to a `Class` object.

Problem
-------

A long-standing gap in built-in core reflection functionality was a direct mapping from the name of a primitive type to its corresponding class object. At least one implementation of this functionality appears privately in the JDK.

Solution
--------

Add a `Class.forPrimitiveName(String)` that maps `"int"` to `int.class`, `"long"` to `long.class`, etc.

Specification
-------------


    --- a/src/java.base/share/classes/java/lang/Class.java
    +++ b/src/java.base/share/classes/java/lang/Class.java
    @@ -438,6 +438,8 @@ public final class Class<T> implements java.io.Serializable,
          * If {@code name} denotes a primitive type or void, for example {@code I},
          * an attempt will be made to locate a user-defined class in the unnamed package
          * whose name is {@code I} instead.
+     * To obtain a {@code Class} object for a named primitive type
+     * such as {@code int} or {@code long} use {@link
+     * #forPrimitiveName(String)}.
          *
          * <p> To obtain the {@code Class} object associated with an array class,
          * the name consists of one or more {@code '['} representing the depth
    @@ -628,6 +630,41 @@ public final class Class<T> implements java.io.Serializable,
             }
         }
     
    +    /**
    +     * {@return the {@code Class} object associated with the
    +     * {@linkplain #isPrimitive() primitive type} of the given name}
    +     * If the argument is not the name of a primitive type, {@code
    +     * null} is returned.
    +     *
    +     * @param primitiveName the name of the primitive type to find
    +     *
    +     * @throws NullPointerException if the argument is {@code null}
    +     *
    +     * @jls 4.2 Primitive Types and Values
    +     * @jls 15.8.2 Class Literals
    +     * @since 22
    +     */
    +    public static Class<?> forPrimitiveName(String primitiveName) {
    +        return switch(primitiveName) {
    +        // Integral types
    +        case "int"     -> int.class;
    +        case "long"    -> long.class;
    +        case "short"   -> short.class;
    +        case "char"    -> char.class;
    +        case "byte"    -> byte.class;
    +
    +        // Floating-point types
    +        case "float"   -> float.class;
    +        case "double"  -> double.class;
    +
    +        // Other types
    +        case "boolean" -> boolean.class;
    +        case "void"    -> void.class;
    +
    +        default        -> null;
    +        };
    +    }
    +
         /**
          * Creates a new instance of the class represented by this {@code Class}
          * object.  The class is instantiated as if by a {@code new}