Create variable names that are CheckStyle compat

core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java

@@ -16,7 +16,6 @@
 
 package com.google.errorprone.bugpatterns;
 
-import static com.google.common.base.Ascii.toLowerCase;
 import static com.google.common.collect.Streams.stream;
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
 import static com.google.errorprone.fixes.SuggestedFix.mergeFixes;
@@ -53,6 +52,7 @@
 import com.sun.source.util.TreePathScanner;
 import com.sun.tools.javac.code.Type;
 import com.sun.tools.javac.code.TypeTag;
+
 import java.util.HashSet;
 import java.util.stream.Stream;
 import javax.inject.Inject;
@@ -162,11 +162,20 @@ public Description matchInstanceOf(InstanceOfTree instanceOfTree, VisitorState s
   private static String generateVariableName(Type targetType, VisitorState state) {
     Type unboxed = state.getTypes().unboxedType(targetType);
     String simpleName = targetType.tsym.getSimpleName().toString();
-    String lowerFirstLetter = toLowerCase(String.valueOf(simpleName.charAt(0)));
-    String camelCased = lowerFirstLetter + simpleName.substring(1);
+    char[] chars = simpleName.toCharArray();
+    boolean priorCharWasUpper = Character.isUpperCase(chars[0]);;
+    chars[0] = Character.toLowerCase(chars[0]);
+    for (int i = 1; i < chars.length - 1; i++) {
+      boolean currentCharIsUpper = Character.isUpperCase(chars[i]);
+      if (currentCharIsUpper && priorCharWasUpper && Character.isUpperCase(chars[i + 1])) {
+        chars[i] = Character.toLowerCase(chars[i]);
+      }
+      priorCharWasUpper = currentCharIsUpper;
+    }
+    String camelCased = new String(chars);
     if (SourceVersion.isKeyword(camelCased)
         || (unboxed != null && unboxed.getTag() != TypeTag.NONE)) {
-      return lowerFirstLetter;
+      return Character.toString(Character.toLowerCase(simpleName.charAt(0)));
     }
     return camelCased;
   }

core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java

@@ -500,6 +500,44 @@ void test(Object o) {
         .doTest();
   }
 
+  @Test
+  public void checkStyleCompliantName() {
+    helper
+            .addInputLines(
+                    "Class.java",
+                    """
+                    import java.io.InterruptedIOException;
+                    import java.sql.SQLException;
+
+                    class Class {
+                      void test(Object e) {
+                        if (e instanceof InterruptedIOException) {
+                          test((InterruptedIOException) e);
+                        } else if (e instanceof SQLException) {
+                          test((SQLException) e);
+                        }
+                      }
+                    }
+                    """)
+            .addOutputLines(
+                    "Class.java",
+                    """
+                    import java.io.InterruptedIOException;
+                    import java.sql.SQLException;                    
+
+                    class Class {
+                      void test(Object e) {
+                        if (e instanceof InterruptedIOException interruptedIoException) {
+                          test(interruptedIoException);
+                        } else if (e instanceof SQLException sqlException) {
+                          test(sqlException);
+                        }
+                      }
+                    }
+                    """)
+            .doTest();
+  }
+
   @Test
   public void recordPatternMatching() {
     assume().that(Runtime.version().feature()).isAtLeast(21);