Summary

Update TypeKind's method names and API specification to address issues with TypeKind.

Problem

1. TypeKind::newarraycode and TypeKind::fromNewArrayCode have name discrepancies.
2. TypeKind::fromDescriptor(String) throws undocumented IndexOutOfBoundsException instead of IllegalArgumentException.

Solution

1. Rename the methods to newarrayCode and fromNewarrayCode. newarray is a whole word as it's the name of an instruction.
2. Specify that TypeKind::fromDescriptor may throw IllegalArgumentException if the descriptor string is invalid (but is not required to do so)

Specification

--- a/src/java.base/share/classes/java/lang/classfile/TypeKind.java
+++ b/src/java.base/share/classes/java/lang/classfile/TypeKind.java
@@ -66,9 +66,12 @@ public enum TypeKind {
     /** {@return the field descriptor character corresponding to this type} */
     public String descriptor() { return descriptor; }

-    /** {@return the code used by the {@code newarray} opcode corresponding to this type} */
-    public int newarraycode() {
-        return newarraycode;
+    /**
+     * {@return the code used by the {@code newarray} opcode corresponding to this type}
+     * @since 23
+     */
+    public int newarrayCode() {
+        return newarrayCode;
     }

     /**
@@ -94,19 +97,21 @@ public TypeKind asLoadable() {
     /**
      * {@return the type kind associated with the array type described by the
      * array code used as an operand to {@code newarray}}
-     * @param newarraycode the operand of the {@code newarray} instruction
+     * @param newarrayCode the operand of the {@code newarray} instruction
+     * @throws IllegalArgumentException if the code is invalid
+     * @since 23
      */
-    public static TypeKind fromNewArrayCode(int newarraycode) {
-        return switch (newarraycode) {
+    public static TypeKind fromNewarrayCode(int newarrayCode) {
+        return switch (newarrayCode) {
             case 4 -> TypeKind.BooleanType;
             case 5 -> TypeKind.CharType;
             case 6 -> TypeKind.FloatType;
@@ -115,15 +120,19 @@ public static TypeKind fromNewArrayCode(int newarraycode) {
     /**
      * {@return the type kind associated with the specified field descriptor}
      * @param s the field descriptor
+     * @throws IllegalArgumentException only if the descriptor is not valid
      */
     public static TypeKind fromDescriptor(CharSequence s) {
+        if (s.isEmpty()) { // implicit null check
+            throw new IllegalArgumentException("Empty descriptor");
+        }
         return switch (s.charAt(0)) {
             case '[', 'L' -> TypeKind.ReferenceType;
             case 'B' -> TypeKind.ByteType;