8342468: Improve API documentation for java.lang.classfile.constantpool

Reviewed-by: asotona

Author: liach

src/java.base/share/classes/java/lang/classfile/BootstrapMethodEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,7 +25,9 @@
 
 package java.lang.classfile;
 
+import java.lang.classfile.attribute.BootstrapMethodsAttribute;
 import java.lang.classfile.constantpool.ConstantPool;
+import java.lang.classfile.constantpool.ConstantPoolBuilder;
 import java.lang.classfile.constantpool.LoadableConstantEntry;
 import java.lang.classfile.constantpool.MethodHandleEntry;
 import java.util.List;
@@ -34,22 +36,40 @@
 
 /**
  * Models an entry in the bootstrap method table.  The bootstrap method table
- * is stored in the {@code BootstrapMethods} attribute, but is modeled by
- * the {@link ConstantPool}, since the bootstrap method table is logically
- * part of the constant pool.
+ * is stored in the {@link BootstrapMethodsAttribute BootstrapMethods}
+ * attribute, but is modeled by the {@link ConstantPool}, since the bootstrap
+ * method table is logically part of the constant pool.
+ * <p>
+ * A bootstrap method entry is composite:
+ * {@snippet lang=text :
+ * // @link substring="BootstrapMethodEntry" target="ConstantPoolBuilder#bsmEntry(MethodHandleEntry, List)" :
+ * BootstrapMethodEntry(
+ *     MethodHandleEntry bootstrapMethod, // @link substring="bootstrapMethod" target="#bootstrapMethod"
+ *     List<LoadableConstantEntry> arguments // @link substring="arguments" target="#arguments()"
+ * )
+ * }
  *
+ * @see ConstantPoolBuilder#bsmEntry ConstantPoolBuilder::bsmEntry
  * @since 24
  */
 public sealed interface BootstrapMethodEntry
         permits BootstrapMethodEntryImpl {
 
     /**
      * {@return the constant pool associated with this entry}
+     *
+     * @apiNote
+     * Given a {@link ConstantPoolBuilder} {@code builder} and a {@code
+     * BootstrapMethodEntry} {@code entry}, use {@link
+     * ConstantPoolBuilder#canWriteDirect
+     * builder.canWriteDirect(entry.constantPool())} instead of object equality
+     * of the constant pool to determine if an entry is compatible.
      */
     ConstantPool constantPool();
 
     /**
-     * {@return the index into the bootstrap method table corresponding to this entry}
+     * {@return the index into the bootstrap method table corresponding to this
+     * entry}
      */
     int bsmIndex();
 

src/java.base/share/classes/java/lang/classfile/ClassFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -140,21 +140,56 @@ static ClassHierarchyResolverOption of(ClassHierarchyResolver classHierarchyReso
 
     /**
      * Option describing whether to preserve the original constant pool when
-     * transforming a classfile.  Reusing the constant pool enables significant
-     * optimizations in processing time and minimizes differences between the
-     * original and transformed classfile, but may result in a bigger classfile
-     * when a classfile is significantly transformed.
-     * Default is {@code SHARED_POOL} to preserve the original constant
-     * pool.
+     * transforming a {@code class} file.  Reusing the constant pool enables
+     * significant optimizations in processing time and minimizes differences
+     * between the original and transformed {@code class} files, but may result
+     * in a bigger transformed {@code class} file when many elements of the
+     * original {@code class} file are dropped and many original constant
+     * pool entries become unused.  Default is {@link #SHARED_POOL} to preserve
+     * the original constant pool.
      *
+     * @see ConstantPoolBuilder
+     * @see #build(ClassEntry, ConstantPoolBuilder, Consumer)
+     * @see #transformClass(ClassModel, ClassTransform)
      * @since 24
      */
     enum ConstantPoolSharingOption implements Option {
 
-        /** Preserves the original constant pool when transforming classfile */
+        /**
+         * Preserves the original constant pool when transforming the {@code
+         * class} file.
+         * <p>
+         * These two transformations below are equivalent:
+         * {@snippet lang=java :
+         * ClassModel originalClass = null; // @replace substring=null; replacement=...
+         * ClassDesc resultClassName = null; // @replace substring=null; replacement=...
+         * ClassTransform classTransform = null; // @replace substring=null; replacement=...
+         * var resultOne = ClassFile.of(ConstantPoolSharingOption.SHARED_POOL)
+         *         .transformClass(originalClass, resultClassName, classTransform);
+         * var resultTwo = ClassFile.of().build(resultClassName, ConstantPoolBuilder.of(originalClass),
+         *         clb -> clb.transform(originalClass, classTransform));
+         * }
+         *
+         * @see ConstantPoolBuilder#of(ClassModel) ConstantPoolBuilder::of(ClassModel)
+         */
         SHARED_POOL,
 
-        /** Creates a new constant pool when transforming classfile */
+        /**
+         * Creates a new constant pool when transforming the {@code class} file.
+         * <p>
+         * These two transformations below are equivalent:
+         * {@snippet lang=java :
+         * ClassModel originalClass = null; // @replace substring=null; replacement=...
+         * ClassDesc resultClassName = null; // @replace substring=null; replacement=...
+         * ClassTransform classTransform = null; // @replace substring=null; replacement=...
+         * var resultOne = ClassFile.of(ConstantPoolSharingOption.NEW_POOL)
+         *         .transformClass(originalClass, resultClassName, classTransform);
+         * var resultTwo = ClassFile.of().build(resultClassName, ConstantPoolBuilder.of(),
+         *         clb -> clb.transform(originalClass, classTransform));
+         * }
+         *
+         * @see ConstantPoolBuilder#of() ConstantPoolBuilder::of()
+         */
         NEW_POOL
     }
 

src/java.base/share/classes/java/lang/classfile/constantpool/AnnotationConstantValueEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -28,10 +28,9 @@
 import java.lang.constant.ConstantDesc;
 
 /**
- * A constant pool entry that may be used by annotation constant values,
- * which includes the four kinds of primitive constants and UTF8 constants.
- * These entries are also the only entries that do not refer to other
- * constant pool entries.
+ * Marker interface for constant pool entries that can represent constant values
+ * associated with elements of annotations.  They are also the only entries that
+ * do not refer to other constant pool entries.
  *
  * @apiNote
  * An annotation constant value entry alone is not sufficient to determine
@@ -40,16 +39,17 @@
  * in {@link AnnotationValue.OfInt}.
  *
  * @see AnnotationValue.OfConstant
+ * @jvms 4.7.16.1 The {@code element_value} structure
  * @sealedGraph
  * @since 24
  */
 public sealed interface AnnotationConstantValueEntry extends PoolEntry
         permits DoubleEntry, FloatEntry, IntegerEntry, LongEntry, Utf8Entry {
 
     /**
-     * {@return the constant value}  The constant value will be an {@link Integer},
-     * {@link Long}, {@link Float}, {@link Double} for the primitive constants,
-     * or {@link String} for UTF8 constants.
+     * {@return the constant value}  The constant value will be an {@link
+     * Integer}, {@link Long}, {@link Float}, {@link Double} for the primitive
+     * constants, or {@link String} for UTF8 constants.
      */
     ConstantDesc constantValue();
 }

src/java.base/share/classes/java/lang/classfile/constantpool/ClassEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -30,33 +30,82 @@
 import jdk.internal.classfile.impl.AbstractPoolEntry;
 
 /**
- * Models a {@code CONSTANT_Class_info} constant in the constant pool of a
- * classfile.
- * @jvms 4.4.1 The CONSTANT_Class_info Structure
+ * Models a {@code CONSTANT_Class_info} structure, representing a reference
+ * type, in the constant pool of a {@code class} file.
+ * <p>
+ * The use of a {@code ClassEntry} is modeled by a {@link ClassDesc} that is not
+ * primitive.  Conversions are through {@link ConstantPoolBuilder#classEntry(
+ * ClassDesc)} and {@link #asSymbol()}.
+ * <p>
+ * A {@code ClassEntry} is composite:
+ * {@snippet lang=text :
+ * // @link substring="ClassEntry" target="ConstantPoolBuilder#classEntry(Utf8Entry)" :
+ * ClassEntry(Utf8Entry name) // @link substring="name" target="#name"
+ * }
+ * where {@code name} represents:
+ * <ul>
+ * <li>The internal form of a binary name (JVMS {@jvms 4.2.1}), if and only if
+ * this {@code ClassEntry} represents a class or interface, such as {@code
+ * java/lang/String} for the {@link String} class.
+ * <li>A field descriptor string (JVMS {@jvms 4.3.2}) representing an array type,
+ * if and only if this {@code ClassEntry} represents an array type, such as
+ * {@code [I} for the {@code int[]} type, or {@code [Ljava/lang/String;} for the
+ * {@code String[]} type.
+ * </ul>
+ * A field descriptor string for an array type can be distinguished by its
+ * leading {@code '['} character.
  *
+ * @apiNote
+ * The internal form of a binary name, where all occurrences of {@code .} in the
+ * name are replaced by {@code /}, is informally known as an <dfn>{@index
+ * "internal name"}</dfn>.  This concept also applies to package names in
+ * addition to class and interface names.
+ *
+ * @see ConstantPoolBuilder#classEntry ConstantPoolBuilder::classEntry
+ * @see ClassDesc
+ * @jvms 4.4.1 The {@code CONSTANT_Class_info} Structure
  * @since 24
  */
 public sealed interface ClassEntry
         extends LoadableConstantEntry
         permits AbstractPoolEntry.ClassEntryImpl {
 
+    /**
+     * {@inheritDoc}
+     * <p>
+     * This is equivalent to {@link #asSymbol() asSymbol()}.
+     */
     @Override
     default ConstantDesc constantValue() {
         return asSymbol();
     }
 
     /**
-     * {@return the UTF8 constant pool entry for the class name}
+     * {@return the {@code Utf8Entry} referred by this structure}  If the
+     * value of the UTF8 starts with a {@code [}, this represents an array type
+     * and the value is a descriptor string; otherwise, this represents a class
+     * or interface and the value is the {@linkplain ##internalname internal
+     * form} of a binary name.
+     *
+     * @see ConstantPoolBuilder#classEntry(Utf8Entry)
+     *      ConstantPoolBuilder::classEntry(Utf8Entry)
      */
     Utf8Entry name();
 
     /**
-     * {@return the class name, as an internal binary name}
+     * {@return the represented reference type, as the {@linkplain
+     * ##internalname internal form} of a binary name or an array descriptor
+     * string}  This is a shortcut for {@link #name() name().stringValue()}.
      */
     String asInternalName();
 
     /**
-     * {@return the class name, as a symbolic descriptor}
+     * {@return the represented reference type, as a symbolic descriptor}  The
+     * returned descriptor is never {@linkplain ClassDesc#isPrimitive()
+     * primitive}.
+     *
+     * @see ConstantPoolBuilder#classEntry(ClassDesc)
+     *      ConstantPoolBuilder::classEntry(ClassDesc)
      */
     ClassDesc asSymbol();
 }

src/java.base/share/classes/java/lang/classfile/constantpool/ConstantDynamicEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -33,30 +33,65 @@
 import jdk.internal.classfile.impl.Util;
 
 /**
- * Models a {@code CONSTANT_Dynamic_info} constant in the constant pool of a
- * classfile.
- * @jvms 4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
+ * Models a {@code CONSTANT_Dynamic_info} structure, representing a <dfn>{@index
+ * "dynamically-computed constant"}</dfn>, in the constant pool of a {@code
+ * class} file.
+ * <p>
+ * The use of a {@code ConstantDynamicEntry} is modeled by a {@link
+ * DynamicConstantDesc}.  Conversions are through {@link #asSymbol()} and {@link
+ * ConstantPoolBuilder#constantDynamicEntry(DynamicConstantDesc)}.
+ * <p>
+ * A dynamic constant entry is composite:
+ * {@snippet lang=text :
+ * // @link substring="ConstantDynamicEntry" target="ConstantPoolBuilder#constantDynamicEntry(BootstrapMethodEntry, NameAndTypeEntry)" :
+ * ConstantDynamicEntry(
+ *     BootstrapMethodEntry bootstrap, // @link substring="bootstrap" target="#bootstrap()"
+ *     NameAndTypeEntry nameAndType // @link substring="nameAndType" target="#nameAndType()"
+ * )
+ * }
+ * where {@link #type() nameAndType.type()} is a {@linkplain #typeSymbol()
+ * field descriptor} string.
  *
+ * @apiNote
+ * A dynamically-computed constant is frequently called a <dfn>{@index "dynamic
+ * constant"}</dfn>, or a <dfn>{@index "condy"}</dfn>, from the abbreviation of
+ * "constant dynamic".
+ *
+ * @see ConstantPoolBuilder#constantDynamicEntry
+ *      ConstantPoolBuilder::constantDynamicEntry
+ * @see DynamicConstantDesc
+ * @see java.lang.invoke##condycon Dynamically-computed constants
+ * @jvms 4.4.10 The {@code CONSTANT_Dynamic_info} and {@code
+ *              CONSTANT_InvokeDynamic_info} Structures
  * @since 24
  */
 public sealed interface ConstantDynamicEntry
         extends DynamicConstantPoolEntry, LoadableConstantEntry
         permits AbstractPoolEntry.ConstantDynamicEntryImpl {
 
     /**
-     * {@return a symbolic descriptor for the dynamic constant's type}
+     * {@return a symbolic descriptor for the {@linkplain #type() field type} of
+     * this dynamically-computed constant}
      */
     default ClassDesc typeSymbol() {
         return Util.fieldTypeSymbol(type());
     }
 
+    /**
+     * {@inheritDoc}
+     * <p>
+     * This is equivalent to {@link #asSymbol() asSymbol()}.
+     */
     @Override
     default ConstantDesc constantValue() {
         return asSymbol();
     }
 
     /**
-     * {@return the symbolic descriptor for the {@code invokedynamic} constant}
+     * {@return a symbolic descriptor for this dynamically-computed constant}
+     *
+     * @see ConstantPoolBuilder#constantDynamicEntry(DynamicConstantDesc)
+     *      ConstantPoolBuilder::constantDynamicEntry(DynamicConstantDesc)
      */
     default DynamicConstantDesc<?> asSymbol() {
         return DynamicConstantDesc.ofNamed(bootstrap().bootstrapMethod().asSymbol(),
@@ -68,10 +103,15 @@ default DynamicConstantDesc<?> asSymbol() {
     }
 
     /**
-     * {@return the type of the constant}
+     * {@inheritDoc}
+     *
+     * @apiNote
+     * The data type of a dynamically-computed constant depends on its
+     * {@linkplain #type() descriptor}, while the data type of all other
+     * constants can be determined by their {@linkplain #tag() constant type}.
      */
     @Override
     default TypeKind typeKind() {
-        return TypeKind.fromDescriptor(type().stringValue());
+        return TypeKind.fromDescriptor(type());
     }
 }