8227046: compiler implementation for sealed classes

8225056: VM support for sealed classes
8227044: javax.lang.model for sealed classes
8227045: Preview APIs support for sealed classes
8227047: Javadoc for sealed types
8245854: JVM TI Specification for sealed classes

Co-authored-by: Harold Seigel <harold.seigel@oracle.com>
Co-authored-by: Jan Lahoda <jan.lahoda@oracle.com>
Reviewed-by: mcimadamore, forax, darcy, dholmes, jlahoda, lfoltan, mchung, sspitsyn, vromero

src/java.base/share/classes/java/lang/Class.java

@@ -201,6 +201,8 @@ public final class Class<T> implements java.io.Serializable,
     private static final int ENUM      = 0x00004000;
     private static final int SYNTHETIC = 0x00001000;
 
+    private static final ClassDesc[] EMPTY_CLASS_DESC_ARRAY = new ClassDesc[0];
+
     private static native void registerNatives();
     static {
         registerNatives();
@@ -4382,4 +4384,69 @@ public final class Class<T> implements java.io.Serializable,
     @HotSpotIntrinsicCandidate
     public native boolean isHidden();
 
+    /**
+     * {@preview Associated with sealed classes, a preview feature of the Java language.
+     *
+     *           This method is associated with <i>sealed classes</i>, a preview
+     *           feature of the Java language. Preview features
+     *           may be removed in a future release, or upgraded to permanent
+     *           features of the Java language.}
+     *
+     * Returns an array containing {@code ClassDesc} objects representing all the
+     * direct subclasses or direct implementation classes permitted to extend or implement this class or interface
+     * if it is sealed. If this {@code Class} object represents a primitive type, {@code void}, an array type,
+     * or a class or interface that is not sealed, an empty array is returned.
+     *
+     * @return an array of class descriptors of all the permitted subclasses of this class or interface
+     *
+     * @jls 8.1 Class Declarations
+     * @jls 9.1 Interface Declarations
+     * @since 15
+     */
+    @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.SEALED_CLASSES, essentialAPI=false)
+    public ClassDesc[] permittedSubclasses() {
+        String[] subclassNames;
+        if (isArray() || isPrimitive() || (subclassNames = getPermittedSubclasses0()).length == 0) {
+            return EMPTY_CLASS_DESC_ARRAY;
+        }
+        ClassDesc[] constants = new ClassDesc[subclassNames.length];
+        int i = 0;
+        for (String subclassName : subclassNames) {
+            try {
+                constants[i++] = ClassDesc.of(subclassName.replace('/', '.'));
+            } catch (IllegalArgumentException iae) {
+                throw new InternalError("Invalid type in permitted subclasses information: " + subclassName, iae);
+            }
+        }
+        return constants;
+    }
+
+    /**
+     * * {@preview Associated with sealed classes, a preview feature of the Java language.
+     *
+     *           This method is associated with <i>sealed classes</i>, a preview
+     *           feature of the Java language. Preview features
+     *           may be removed in a future release, or upgraded to permanent
+     *           features of the Java language.}
+     *
+     * Returns {@code true} if and only if this {@code Class} object represents a sealed class or interface.
+     * If this {@code Class} object represents a primitive type, {@code void}, or an array type, this method returns
+     * {@code false}.
+     *
+     * @return {@code true} if and only if this {@code Class} object represents a sealed class or interface.
+     *
+     * @jls 8.1 Class Declarations
+     * @jls 9.1 Interface Declarations
+     * @since 15
+     */
+    @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.SEALED_CLASSES, essentialAPI=false)
+    @SuppressWarnings("preview")
+    public boolean isSealed() {
+        if (isArray() || isPrimitive()) {
+            return false;
+        }
+        return permittedSubclasses().length != 0;
+    }
+
+    private native String[] getPermittedSubclasses0();
 }

src/java.base/share/classes/jdk/internal/PreviewFeature.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, 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
@@ -63,6 +63,7 @@ public @interface PreviewFeature {
         // necessary for PreviewFeature in JDK 15 to declare the enum constant.
         TEXT_BLOCKS,
         RECORDS,
+        SEALED_CLASSES,
         ;
     }
 }

src/java.base/share/classes/jdk/internal/org/objectweb/asm/ClassReader.java

@@ -499,8 +499,8 @@ public class ClassReader {
         String nestHostClass = null;
         // - The offset of the NestMembers attribute, or 0.
         int nestMembersOffset = 0;
-        // - The offset of the PermittedSubtypes attribute, or 0
-        int permittedSubtypesOffset = 0;
+        // - The offset of the PermittedSubclasses attribute, or 0
+        int permittedSubclassesOffset = 0;
         // - The offset of the Record attribute, or 0.
         int recordOffset = 0;
         // - The non standard attributes (linked with their {@link Attribute#nextAttribute} field).
@@ -525,8 +525,8 @@ public class ClassReader {
                 nestHostClass = readClass(currentAttributeOffset, charBuffer);
             } else if (Constants.NEST_MEMBERS.equals(attributeName)) {
                 nestMembersOffset = currentAttributeOffset;
-            } else if (Constants.PERMITTED_SUBTYPES.equals(attributeName)) {
-                permittedSubtypesOffset = currentAttributeOffset;
+            } else if (Constants.PERMITTED_SUBCLASSES.equals(attributeName)) {
+                permittedSubclassesOffset = currentAttributeOffset;
             } else if (Constants.SIGNATURE.equals(attributeName)) {
                 signature = readUTF8(currentAttributeOffset, charBuffer);
             } else if (Constants.RUNTIME_VISIBLE_ANNOTATIONS.equals(attributeName)) {
@@ -704,14 +704,14 @@ public class ClassReader {
             }
         }
 
-        // Visit the PermittedSubtypes attribute.
-        if (permittedSubtypesOffset != 0) {
-            int numberOfPermittedSubtypes = readUnsignedShort(permittedSubtypesOffset);
-            int currentPermittedSubtypeOffset = permittedSubtypesOffset + 2;
-            while (numberOfPermittedSubtypes-- > 0) {
-                classVisitor.visitPermittedSubtypeExperimental(
-                        readClass(currentPermittedSubtypeOffset, charBuffer));
-                currentPermittedSubtypeOffset += 2;
+        // Visit the PermittedSubclasses attribute.
+        if (permittedSubclassesOffset != 0) {
+            int numberOfPermittedSubclasses = readUnsignedShort(permittedSubclassesOffset);
+            int currentPermittedSubclassOffset = permittedSubclassesOffset + 2;
+            while (numberOfPermittedSubclasses-- > 0) {
+                classVisitor.visitPermittedSubclassExperimental(
+                        readClass(currentPermittedSubclassOffset, charBuffer));
+                currentPermittedSubclassOffset += 2;
             }
         }
 

src/java.base/share/classes/jdk/internal/org/objectweb/asm/ClassVisitor.java

@@ -61,7 +61,7 @@ package jdk.internal.org.objectweb.asm;
 /**
  * A visitor to visit a Java class. The methods of this class must be called in the following order:
  * {@code visit} [ {@code visitSource} ] [ {@code visitModule} ][ {@code visitNestHost} ][ {@code
- * visitPermittedSubtype} ][ {@code visitOuterClass} ] ( {@code visitAnnotation} | {@code
+ * visitPermittedSubclass} ][ {@code visitOuterClass} ] ( {@code visitAnnotation} | {@code
  * visitTypeAnnotation} | {@code visitAttribute} )* ( {@code visitNestMember} | {@code
  * visitInnerClass} | {@code visitField} | {@code visitMethod} )* {@code visitEnd}.
  *
@@ -287,19 +287,19 @@ public abstract class ClassVisitor {
 
     /**
       * <b>Experimental, use at your own risk. This method will be renamed when it becomes stable, this
-      * will break existing code using it</b>. Visits a permitted subtypes. A permitted subtypes is one
-      * of the allowed subtypes of the current class.
+      * will break existing code using it</b>. Visits a permitted subclass. A permitted subclass is one
+      * of the allowed subclasses of the current class.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
         if (api != Opcodes.ASM9_EXPERIMENTAL) {
             throw new UnsupportedOperationException("This feature requires ASM9_EXPERIMENTAL");
         }
         if (cv != null) {
-            cv.visitPermittedSubtypeExperimental(permittedSubtype);
+            cv.visitPermittedSubclassExperimental(permittedSubclass);
         }
     }
 

src/java.base/share/classes/jdk/internal/org/objectweb/asm/ClassWriter.java

@@ -208,11 +208,11 @@ public class ClassWriter extends ClassVisitor {
     /** The 'classes' array of the NestMembers attribute, or {@literal null}. */
     private ByteVector nestMemberClasses;
 
-    /** The number_of_classes field of the PermittedSubtypes attribute, or 0. */
-    private int numberOfPermittedSubtypeClasses;
+    /** The number_of_classes field of the PermittedSubclasses attribute, or 0. */
+    private int numberOfPermittedSubclassClasses;
 
-    /** The 'classes' array of the PermittedSubtypes attribute, or {@literal null}. */
-    private ByteVector permittedSubtypeClasses;
+    /** The 'classes' array of the PermittedSubclasses attribute, or {@literal null}. */
+    private ByteVector permittedSubclassClasses;
 
     /**
       * The record components of this class, stored in a linked list of {@link RecordComponentWriter}
@@ -406,17 +406,17 @@ public class ClassWriter extends ClassVisitor {
     /**
       * <b>Experimental, use at your own risk.</b>
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public final void visitPermittedSubtypeExperimental(final String permittedSubtype) {
-        if (permittedSubtypeClasses == null) {
-            permittedSubtypeClasses = new ByteVector();
+    public final void visitPermittedSubclassExperimental(final String permittedSubclass) {
+        if (permittedSubclassClasses == null) {
+            permittedSubclassClasses = new ByteVector();
         }
-        ++numberOfPermittedSubtypeClasses;
-        permittedSubtypeClasses.putShort(symbolTable.addConstantClass(permittedSubtype).index);
+        ++numberOfPermittedSubclassClasses;
+        permittedSubclassClasses.putShort(symbolTable.addConstantClass(permittedSubclass).index);
     }
 
     @Override
@@ -607,10 +607,10 @@ public class ClassWriter extends ClassVisitor {
             size += 8 + nestMemberClasses.length;
             symbolTable.addConstantUtf8(Constants.NEST_MEMBERS);
         }
-        if (permittedSubtypeClasses != null) {
+        if (permittedSubclassClasses != null) {
             ++attributesCount;
-            size += 8 + permittedSubtypeClasses.length;
-            symbolTable.addConstantUtf8(Constants.PERMITTED_SUBTYPES);
+            size += 8 + permittedSubclassClasses.length;
+            symbolTable.addConstantUtf8(Constants.PERMITTED_SUBCLASSES);
         }
         int recordComponentCount = 0;
         int recordSize = 0;
@@ -729,12 +729,12 @@ public class ClassWriter extends ClassVisitor {
                     .putShort(numberOfNestMemberClasses)
                     .putByteArray(nestMemberClasses.data, 0, nestMemberClasses.length);
         }
-        if (permittedSubtypeClasses != null) {
+        if (permittedSubclassClasses != null) {
             result
-                    .putShort(symbolTable.addConstantUtf8(Constants.PERMITTED_SUBTYPES))
-                    .putInt(permittedSubtypeClasses.length + 2)
-                    .putShort(numberOfPermittedSubtypeClasses)
-                    .putByteArray(permittedSubtypeClasses.data, 0, permittedSubtypeClasses.length);
+                    .putShort(symbolTable.addConstantUtf8(Constants.PERMITTED_SUBCLASSES))
+                    .putInt(permittedSubclassClasses.length + 2)
+                    .putShort(numberOfPermittedSubclassClasses)
+                    .putByteArray(permittedSubclassClasses.data, 0, permittedSubclassClasses.length);
         }
         if ((accessFlags & Opcodes.ACC_RECORD) != 0 || firstRecordComponent != null) {
             result
@@ -783,8 +783,8 @@ public class ClassWriter extends ClassVisitor {
         nestHostClassIndex = 0;
         numberOfNestMemberClasses = 0;
         nestMemberClasses = null;
-        numberOfPermittedSubtypeClasses = 0;
-        permittedSubtypeClasses = null;
+        numberOfPermittedSubclassClasses = 0;
+        permittedSubclassClasses = null;
         firstRecordComponent = null;
         lastRecordComponent = null;
         firstAttribute = null;

src/java.base/share/classes/jdk/internal/org/objectweb/asm/Constants.java

@@ -104,7 +104,7 @@ final class Constants {
     static final String MODULE_MAIN_CLASS = "ModuleMainClass";
     static final String NEST_HOST = "NestHost";
     static final String NEST_MEMBERS = "NestMembers";
-    static final String PERMITTED_SUBTYPES = "PermittedSubtypes";
+    static final String PERMITTED_SUBCLASSES = "PermittedSubclasses";
     static final String RECORD = "Record";
 
     // ASM specific access flags.

src/java.base/share/classes/jdk/internal/org/objectweb/asm/commons/ClassRemapper.java

@@ -252,13 +252,13 @@ public class ClassRemapper extends ClassVisitor {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
-        super.visitPermittedSubtypeExperimental(remapper.mapType(permittedSubtype));
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
+        super.visitPermittedSubclassExperimental(remapper.mapType(permittedSubclass));
     }
 
     /**

src/java.base/share/classes/jdk/internal/org/objectweb/asm/tree/ClassNode.java

@@ -160,12 +160,12 @@ public class ClassNode extends ClassVisitor {
 
     /**
       * <b>Experimental, use at your own risk. This method will be renamed when it becomes stable, this
-      * will break existing code using it</b>. The internal names of the permitted subtypes of this
+      * will break existing code using it</b>. The internal names of the permitted subclasses of this
       * class. May be {@literal null}.
       *
       * @deprecated this API is experimental.
       */
-    @Deprecated public List<String> permittedSubtypesExperimental;
+    @Deprecated public List<String> permittedSubclassesExperimental;
 
     /** The record components of this class. May be {@literal null}. */
     public List<RecordComponentNode> recordComponents;
@@ -284,13 +284,13 @@ public class ClassNode extends ClassVisitor {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
-        permittedSubtypesExperimental = Util.add(permittedSubtypesExperimental, permittedSubtype);
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
+        permittedSubclassesExperimental = Util.add(permittedSubclassesExperimental, permittedSubclass);
     }
 
     @Override
@@ -351,7 +351,7 @@ public class ClassNode extends ClassVisitor {
       */
     @SuppressWarnings("deprecation")
     public void check(final int api) {
-        if (api != Opcodes.ASM9_EXPERIMENTAL && permittedSubtypesExperimental != null) {
+        if (api != Opcodes.ASM9_EXPERIMENTAL && permittedSubclassesExperimental != null) {
             throw new UnsupportedClassVersionException();
         }
         if (api < Opcodes.ASM8 && ((access & Opcodes.ACC_RECORD) != 0 || recordComponents != null)) {
@@ -473,10 +473,10 @@ public class ClassNode extends ClassVisitor {
                 classVisitor.visitNestMember(nestMembers.get(i));
             }
         }
-        // Visit the permitted subtypes.
-        if (permittedSubtypesExperimental != null) {
-            for (int i = 0, n = permittedSubtypesExperimental.size(); i < n; ++i) {
-                classVisitor.visitPermittedSubtypeExperimental(permittedSubtypesExperimental.get(i));
+        // Visit the permitted subclass.
+        if (permittedSubclassesExperimental != null) {
+            for (int i = 0, n = permittedSubclassesExperimental.size(); i < n; ++i) {
+                classVisitor.visitPermittedSubclassExperimental(permittedSubclassesExperimental.get(i));
             }
         }
         // Visit the inner classes.

src/java.base/share/classes/jdk/internal/org/objectweb/asm/util/ASMifier.java

@@ -357,15 +357,15 @@ public class ASMifier extends Printer {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
         stringBuilder.setLength(0);
-        stringBuilder.append("classWriter.visitPermittedSubtypeExperimental(");
-        appendConstant(permittedSubtype);
+        stringBuilder.append("classWriter.visitPermittedSubclassExperimental(");
+        appendConstant(permittedSubclass);
         stringBuilder.append(END_PARAMETERS);
         text.add(stringBuilder.toString());
     }

src/java.base/share/classes/jdk/internal/org/objectweb/asm/util/CheckClassAdapter.java

@@ -356,15 +356,15 @@ public class CheckClassAdapter extends ClassVisitor {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
         checkState();
-        CheckMethodAdapter.checkInternalName(version, permittedSubtype, "permittedSubtype");
-        super.visitPermittedSubtypeExperimental(permittedSubtype);
+        CheckMethodAdapter.checkInternalName(version, permittedSubclass, "permittedSubclass");
+        super.visitPermittedSubclassExperimental(permittedSubclass);
     }
 
     @Override

src/java.base/share/classes/jdk/internal/org/objectweb/asm/util/Printer.java

@@ -488,15 +488,15 @@ public abstract class Printer {
       * <b>Experimental, use at your own risk. This method will be renamed when it becomes stable, this
       * will break existing code using it</b>.
       *
-      * <p>Visits a permitted subtypes. A permitted subtypes is one of the allowed subtypes of the
+      * <p>Visits a permitted subclass. A permitted subtclass is one of the allowed subclasses of the
       * current class. See {@link
-      * jdk.internal.org.objectweb.asm.ClassVisitor#visitPermittedSubtypeExperimental(String)}.
+      * jdk.internal.org.objectweb.asm.ClassVisitor#visitPermittedSubclassExperimental(String)}.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
         throw new UnsupportedOperationException(UNSUPPORTED_OPERATION);
     }
 

src/java.base/share/classes/jdk/internal/org/objectweb/asm/util/Textifier.java

@@ -340,15 +340,15 @@ public class Textifier extends Printer {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
         stringBuilder.setLength(0);
-        stringBuilder.append(tab).append("PERMITTEDSUBTYPE ");
-        appendDescriptor(INTERNAL_NAME, permittedSubtype);
+        stringBuilder.append(tab).append("PERMITTEDSUBCLASS ");
+        appendDescriptor(INTERNAL_NAME, permittedSubclass);
         stringBuilder.append('\n');
         text.add(stringBuilder.toString());
     }

src/java.base/share/classes/jdk/internal/org/objectweb/asm/util/TraceClassVisitor.java

@@ -222,14 +222,14 @@ public final class TraceClassVisitor extends ClassVisitor {
     /**
       * <b>Experimental, use at your own risk.</b>.
       *
-      * @param permittedSubtype the internal name of a permitted subtype.
+      * @param permittedSubclass the internal name of a permitted subclass.
       * @deprecated this API is experimental.
       */
     @Override
     @Deprecated
-    public void visitPermittedSubtypeExperimental(final String permittedSubtype) {
-        p.visitPermittedSubtypeExperimental(permittedSubtype);
-        super.visitPermittedSubtypeExperimental(permittedSubtype);
+    public void visitPermittedSubclassExperimental(final String permittedSubclass) {
+        p.visitPermittedSubclassExperimental(permittedSubclass);
+        super.visitPermittedSubclassExperimental(permittedSubclass);
     }
 
     @Override

src/java.base/share/native/libjava/Class.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2020, 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
@@ -81,6 +81,7 @@ static JNINativeMethod methods[] = {
     {"getNestMembers0",      "()[" CLS,     (void *)&JVM_GetNestMembers},
     {"getRecordComponents0", "()[" RC,      (void *)&JVM_GetRecordComponents},
     {"isRecord0",            "()Z",         (void *)&JVM_IsRecord},
+    {"getPermittedSubclasses0", "()[" STR,  (void *)&JVM_GetPermittedSubclasses},
 };
 
 #undef OBJ