8355335: Avoid pattern matching switches in core ClassFile API

src/java.base/share/classes/jdk/internal/classfile/impl/BlockCodeBuilderImpl.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
@@ -72,11 +72,10 @@ public boolean isEmpty() {
     }
 
     private int topLocal(CodeBuilder parent) {
-        return switch (parent) {
-            case BlockCodeBuilderImpl b -> b.topLocal;
-            case ChainedCodeBuilder b -> b.terminal.curTopLocal();
-            case TerminalCodeBuilder b -> b.curTopLocal();
-        };
+        if (parent instanceof BlockCodeBuilderImpl bcb) {
+            return bcb.topLocal;
+        }
+        return findTerminal(parent).curTopLocal();
     }
 
     @Override

src/java.base/share/classes/jdk/internal/classfile/impl/ChainedClassBuilder.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
@@ -39,10 +39,8 @@ public final class ChainedClassBuilder
     public ChainedClassBuilder(ClassBuilder downstream,
                                Consumer<ClassElement> consumer) {
         this.consumer = consumer;
-        this.terminal = switch (downstream) {
-            case ChainedClassBuilder cb -> cb.terminal;
-            case DirectClassBuilder db -> db;
-        };
+        this.terminal = downstream instanceof ChainedClassBuilder ccb ?
+                ccb.terminal : (DirectClassBuilder) downstream;
     }
 
     @Override

src/java.base/share/classes/jdk/internal/classfile/impl/ChainedFieldBuilder.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
@@ -38,10 +38,8 @@ public final class ChainedFieldBuilder implements FieldBuilder {
     public ChainedFieldBuilder(FieldBuilder downstream,
                                Consumer<FieldElement> consumer) {
         this.consumer = consumer;
-        this.terminal = switch (downstream) {
-            case ChainedFieldBuilder cb -> cb.terminal;
-            case TerminalFieldBuilder tb -> tb;
-        };
+        this.terminal = downstream instanceof ChainedFieldBuilder cfb ?
+                cfb.terminal : (TerminalFieldBuilder) downstream;
     }
 
     @Override

src/java.base/share/classes/jdk/internal/classfile/impl/ChainedMethodBuilder.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
@@ -41,10 +41,8 @@ public final class ChainedMethodBuilder implements MethodBuilder {
     public ChainedMethodBuilder(MethodBuilder downstream,
                                 Consumer<MethodElement> consumer) {
         this.consumer = consumer;
-        this.terminal = switch (downstream) {
-            case ChainedMethodBuilder cb -> cb.terminal;
-            case TerminalMethodBuilder tb -> tb;
-        };
+        this.terminal = downstream instanceof ChainedMethodBuilder cmb ?
+                cmb.terminal : (TerminalMethodBuilder) downstream;
     }
 
     @Override

src/java.base/share/classes/jdk/internal/classfile/impl/CodeImpl.java

@@ -264,14 +264,16 @@ private void inflateJumpTargets() {
                 //fallback to jump targets inflation without StackMapTableAttribute
                 for (int pos=codeStart; pos<codeEnd; ) {
                     var i = bcToInstruction(classReader.readU1(pos), pos);
-                    switch (i) {
-                        case BranchInstruction br -> br.target();
-                        case DiscontinuedInstruction.JsrInstruction jsr -> jsr.target();
-                        case LookupSwitchInstruction ls -> {
+                    switch (i.opcode().kind()) {
+                        case BRANCH -> ((BranchInstruction) i).target();
+                        case DISCONTINUED_JSR -> ((DiscontinuedInstruction.JsrInstruction) i).target();
+                        case LOOKUP_SWITCH -> {
+                            var ls = (LookupSwitchInstruction) i;
                             ls.defaultTarget();
                             ls.cases();
                         }
-                        case TableSwitchInstruction ts -> {
+                        case TABLE_SWITCH -> {
+                            var ts = (TableSwitchInstruction) i;
                             ts.defaultTarget();
                             ts.cases();
                         }

src/java.base/share/classes/jdk/internal/classfile/impl/NonterminalCodeBuilder.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
@@ -35,10 +35,12 @@ public abstract sealed class NonterminalCodeBuilder implements CodeBuilder
 
     public NonterminalCodeBuilder(CodeBuilder parent) {
         this.parent = parent;
-        this.terminal = switch (parent) {
-            case NonterminalCodeBuilder cb -> cb.terminal;
-            case TerminalCodeBuilder cb -> cb;
-        };
+        this.terminal = findTerminal(parent);
+    }
+
+    static TerminalCodeBuilder findTerminal(CodeBuilder cob) {
+        return cob instanceof NonterminalCodeBuilder ncb ?
+                ncb.terminal : (TerminalCodeBuilder) cob;
     }
 
     @Override