Side-effect annotations

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

@@ -2174,6 +2174,7 @@ private static class CaseInsensitiveComparator
         @java.io.Serial
         private static final long serialVersionUID = 8575799808933029326L;
 
+        @Pure
         public int compare(String s1, String s2) {
             byte[] v1 = s1.value;
             byte[] v2 = s2.value;
@@ -2617,6 +2618,7 @@ public int hashCode() {
      *          {@code endIndex}.
      * @since   21
      */
+    @Pure
     public int indexOf(int ch, int beginIndex, int endIndex) {
         checkBoundsBeginEnd(beginIndex, endIndex, length());
         return isLatin1() ? StringLatin1.indexOf(value, ch, beginIndex, endIndex)
@@ -2781,6 +2783,7 @@ public int indexOf(int ch, int beginIndex, int endIndex) {
      *          {@code endIndex}.
      * @since   21
      */
+    @Pure
     public int indexOf(String str, int beginIndex, int endIndex) {
         if (str.length() == 1) {
             /* Simple optimization, can be omitted without behavioral impact */
@@ -3474,6 +3477,7 @@ public String replace(@GuardSatisfied CharSequence target, @GuardSatisfied CharS
      *
      * @since   21
      */
+    @SideEffectFree
     public String[] splitWithDelimiters(String regex, int limit) {
         return split(regex, limit, true);
     }
@@ -4093,6 +4097,7 @@ public boolean isBlank() {
      *
      * @since 11
      */
+    @SideEffectFree
     public Stream<String> lines() {
         return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
     }
@@ -4490,6 +4495,7 @@ public <R> R transform(Function<? super String, ? extends R> f) {
      * @return an IntStream of char values from this sequence
      * @since 9
      */
+    @SideEffectFree
     @Override
     public IntStream chars() {
         return StreamSupport.intStream(
@@ -4510,6 +4516,7 @@ public IntStream chars() {
      * @return an IntStream of Unicode code points from this sequence
      * @since 9
      */
+    @SideEffectFree
     @Override
     public IntStream codePoints() {
         return StreamSupport.intStream(
@@ -5112,6 +5119,7 @@ static String valueOfCodePoint(int codePoint) {
      * @return an {@link Optional} describing the {@linkplain String} instance
      * @since 12
      */
+    @SideEffectFree
     @Override
     public Optional<String> describeConstable() {
         return Optional.of(this);
@@ -5125,6 +5133,7 @@ public Optional<String> describeConstable() {
      * @return the {@linkplain String} instance
      * @since 12
      */
+    @Pure
     @Override
     public String resolveConstantDesc(MethodHandles.Lookup lookup) {
         return this;

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

@@ -208,6 +208,7 @@ public final class StringBuffer
      *
      * @since 11
      */
+    @SideEffectFree
     @Override
     public synchronized int compareTo(StringBuffer another) {
         return super.compareTo(another);
@@ -219,6 +220,7 @@ public synchronized int compareTo(StringBuffer another) {
         return count;
     }
 
+    @Pure
     @Override
     public synchronized @NonNegative int capacity() {
         return super.capacity();
@@ -252,6 +254,7 @@ public synchronized void setLength(@NonNegative int newLength) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @see        #length()
      */
+    @Pure
     @Override
     public synchronized char charAt(int index) {
         return super.charAt(index);
@@ -261,6 +264,7 @@ public synchronized char charAt(int index) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @since      1.5
      */
+    @Pure
     @Override
     public synchronized int codePointAt(int index) {
         return super.codePointAt(index);
@@ -270,6 +274,7 @@ public synchronized int codePointAt(int index) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @since     1.5
      */
+    @Pure
     @Override
     public synchronized int codePointBefore(int index) {
         return super.codePointBefore(index);
@@ -279,6 +284,7 @@ public synchronized int codePointBefore(int index) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @since     1.5
      */
+    @Pure
     @Override
     public synchronized int codePointCount(int beginIndex, int endIndex) {
         return super.codePointCount(beginIndex, endIndex);
@@ -288,6 +294,7 @@ public synchronized int codePointCount(int beginIndex, int endIndex) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @since     1.5
      */
+    @Pure
     @Override
     public synchronized int offsetByCodePoints(int index, int codePointOffset) {
         return super.offsetByCodePoints(index, codePointOffset);
@@ -296,6 +303,7 @@ public synchronized int offsetByCodePoints(int index, int codePointOffset) {
     /**
      * @throws IndexOutOfBoundsException {@inheritDoc}
      */
+    @SideEffectFree
     @Override
     public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
                                       @IndexOrHigh({"#3"}) int dstBegin)
@@ -516,6 +524,7 @@ public synchronized StringBuffer replace(int start, int end, String str) {
      * @throws StringIndexOutOfBoundsException {@inheritDoc}
      * @since      1.2
      */
+    @SideEffectFree
     @Override
     public synchronized String substring(int start) {
         return substring(start, count);
@@ -525,6 +534,7 @@ public synchronized String substring(int start) {
      * @throws IndexOutOfBoundsException {@inheritDoc}
      * @since      1.4
      */
+    @SideEffectFree
     @Override
     public synchronized CharSequence subSequence(int start, int end) {
         return super.substring(start, end);
@@ -534,6 +544,7 @@ public synchronized CharSequence subSequence(int start, int end) {
      * @throws StringIndexOutOfBoundsException {@inheritDoc}
      * @since      1.2
      */
+    @SideEffectFree
     @Override
     public synchronized String substring(int start, int end) {
         return super.substring(start, end);
@@ -726,7 +737,6 @@ public synchronized StringBuffer reverse() {
         return this;
     }
 
-    @SideEffectFree
     /**
      * @throws IllegalArgumentException {@inheritDoc}
      *
@@ -749,6 +759,7 @@ public synchronized StringBuffer repeat(CharSequence cs, int count) {
         return this;
     }
 
+    @SideEffectFree
     @Override
     @IntrinsicCandidate
     public synchronized String toString(@GuardSatisfied StringBuffer this) {

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

@@ -176,6 +176,7 @@ public StringBuilder(CharSequence seq) {
      *
      * @since 11
      */
+    @SideEffectFree
     @Override
     public int compareTo(StringBuilder another) {
         return super.compareTo(another);
@@ -493,12 +494,12 @@ public StringBuilder reverse() {
         return this;
     }
 
-    @SideEffectFree
     /**
      * @throws IllegalArgumentException {@inheritDoc}
      *
      * @since 21
      */
+    @SideEffectsOnly("this")
     @Override
     public StringBuilder repeat(int codePoint, int count) {
         super.repeat(codePoint, count);
@@ -510,12 +511,14 @@ public StringBuilder repeat(int codePoint, int count) {
      *
      * @since 21
      */
+    @SideEffectsOnly("this")
     @Override
     public StringBuilder repeat(CharSequence cs, int count) {
         super.repeat(cs, count);
         return this;
     }
 
+    @SideEffectFree
     @Override
     @IntrinsicCandidate
     public @PolyRegex String toString(@GuardSatisfied @PolyRegex StringBuilder this) {