Annotate comparison methods as @Pure

src/java.base/share/classes/com/sun/crypto/provider/PBKDF2KeyImpl.java

@@ -168,6 +168,7 @@ public int hashCode() {
                       prf.getAlgorithm().toLowerCase(Locale.ENGLISH).hashCode();
                 }
                 @Override
+                @Pure
                 public boolean equals(Object obj) {
                     if (this == obj) return true;
                     if (this.getClass() != obj.getClass()) return false;

src/java.base/share/classes/java/io/FileSystem.java

@@ -28,6 +28,7 @@
 import org.checkerframework.checker.index.qual.IndexOrHigh;
 import org.checkerframework.checker.interning.qual.UsesObjectEquals;
 import org.checkerframework.checker.signedness.qual.SignedPositive;
+import org.checkerframework.dataflow.qual.Pure;
 import org.checkerframework.framework.qual.AnnotatedFor;
 
 import java.lang.annotation.Native;
@@ -242,6 +243,7 @@ public abstract boolean createFileExclusively(String pathname)
     /**
      * Compare two abstract pathnames lexicographically.
      */
+    @Pure
     public abstract int compare(File f1, File f2);
 
     /**

src/java.base/share/classes/java/io/InvalidClassException.java

@@ -107,6 +107,7 @@ public InvalidClassException(String cname, @Nullable String reason, @Nullable Th
     /**
      * Produce the message and include the classname, if present.
      */
+    @SideEffectFree
     @Override
     public String getMessage() {
         if (classname == null)

src/java.base/share/classes/java/io/ObjectStreamClass.java

@@ -28,6 +28,7 @@
 import org.checkerframework.checker.lock.qual.GuardSatisfied;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.checker.signature.qual.BinaryName;
+import org.checkerframework.dataflow.qual.Pure;
 import org.checkerframework.dataflow.qual.SideEffectFree;
 import org.checkerframework.framework.qual.AnnotatedFor;
 
@@ -1779,6 +1780,7 @@ private static long computeDefaultSUID(Class<?> cl) {
                 fieldSigs[i] = new MemberSignature(fields[i]);
             }
             Arrays.sort(fieldSigs, new Comparator<>() {
+                @Pure
                 public int compare(MemberSignature ms1, MemberSignature ms2) {
                     return ms1.name.compareTo(ms2.name);
                 }
@@ -1810,6 +1812,7 @@ public int compare(MemberSignature ms1, MemberSignature ms2) {
                 consSigs[i] = new MemberSignature(cons[i]);
             }
             Arrays.sort(consSigs, new Comparator<>() {
+                @Pure
                 public int compare(MemberSignature ms1, MemberSignature ms2) {
                     return ms1.signature.compareTo(ms2.signature);
                 }
@@ -1833,6 +1836,7 @@ public int compare(MemberSignature ms1, MemberSignature ms2) {
                 methSigs[i] = new MemberSignature(methods[i]);
             }
             Arrays.sort(methSigs, new Comparator<>() {
+                @Pure
                 public int compare(MemberSignature ms1, MemberSignature ms2) {
                     int comp = ms1.name.compareTo(ms2.name);
                     if (comp == 0) {
@@ -2166,6 +2170,7 @@ public int hashCode() {
             return hash;
         }
 
+        @Pure
         public boolean equals(@Nullable Object obj) {
             return obj == this ||
                    obj instanceof FieldReflectorKey other &&
@@ -2294,6 +2299,7 @@ public final int hashCode() {
             }
 
             @Override
+            @Pure
             public final boolean equals(@Nullable Object obj) {
                 if (!(obj instanceof Key other)) return false;
                 int n = length();

src/java.base/share/classes/java/io/OptionalDataException.java

@@ -24,6 +24,7 @@
  */
 package java.io;
 
+import org.checkerframework.dataflow.qual.SideEffectFree;
 import org.checkerframework.framework.qual.AnnotatedFor;
 
 /**
@@ -55,6 +56,7 @@ public class OptionalDataException extends ObjectStreamException {
     /*
      * Create an {@code OptionalDataException} with a length.
      */
+    @SideEffectFree
     OptionalDataException(int len) {
         eof = false;
         length = len;
@@ -64,6 +66,7 @@ public class OptionalDataException extends ObjectStreamException {
      * Create an {@code OptionalDataException} signifying no
      * more primitive data is available.
      */
+    @SideEffectFree
     OptionalDataException(boolean end) {
         length = 0;
         eof = end;

src/java.base/share/classes/java/io/UncheckedIOException.java

@@ -25,6 +25,7 @@
 package java.io;
 
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.dataflow.qual.Pure;
 import org.checkerframework.dataflow.qual.SideEffectFree;
 import org.checkerframework.framework.qual.AnnotatedFor;
 
@@ -75,6 +76,7 @@ public UncheckedIOException(IOException cause) {
      *
      * @return  the {@code IOException} which is the cause of this exception.
      */
+    @Pure
     @Override
     public IOException getCause() {
         return (IOException) super.getCause();

src/java.base/share/classes/java/io/WriteAbortedException.java

@@ -26,6 +26,7 @@
 package java.io;
 
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.dataflow.qual.Pure;
 import org.checkerframework.dataflow.qual.SideEffectFree;
 import org.checkerframework.framework.qual.AnnotatedFor;
 
@@ -74,6 +75,7 @@ public WriteAbortedException(@Nullable String s, @Nullable Exception ex) {
      * Produce the message and include the message from the nested
      * exception, if there is one.
      */
+    @SideEffectFree
     public String getMessage() {
         if (detail == null)
             return super.getMessage();
@@ -88,6 +90,7 @@ public String getMessage() {
      *          which may be null.
      * @since   1.4
      */
+    @Pure
     @Override
     public @Nullable Throwable getCause() {
         return detail;