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8369921: [lworld] Remove caches of primitive wrapper classes #1685

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8369921: [lworld] Remove caches of primitive wrapper classes #1685

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5b7e32a
8369921: [lworld] Remove caches of primitive wrapper classes
RogerRiggs Oct 16, 2025
10eab81
Review suggestions to put constant locals into non-preview block
RogerRiggs Oct 20, 2025
7a94a94
One more assignment into the !Preview block in Short.
RogerRiggs Oct 24, 2025
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25 changes: 19 additions & 6 deletions src/java.base/share/classes/java/lang/Byte.java
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Expand Up @@ -26,6 +26,7 @@
package java.lang;

import jdk.internal.misc.CDS;
import jdk.internal.misc.PreviewFeatures;
import jdk.internal.value.DeserializeConstructor;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import jdk.internal.vm.annotation.Stable;
Expand Down Expand Up @@ -142,11 +143,23 @@ private ByteCache() {}
/**
* Returns a {@code Byte} instance representing the specified
* {@code byte} value.
* If a new {@code Byte} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Byte(byte)}, as this method is likely to yield
* significantly better space and time performance since
* all byte values are cached.
* <div class="preview-block">
* <div class="preview-comment">
* <p>
* - When preview features are NOT enabled, {@code Byte} is an identity class.
* If a new {@code Byte} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Byte(byte)}, as this method is likely to yield
* significantly better space and time performance since
* all byte values are cached.
* </p>
* <p>
* - When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
* The {@code valueOf} behavior is the same as invoking the constructor,
* whether cached or not.
* </p>
* </div>
* </div>
*
* @param b a byte value.
* @return a {@code Byte} instance representing {@code b}.
Expand All @@ -156,7 +169,7 @@ private ByteCache() {}
@DeserializeConstructor
public static Byte valueOf(byte b) {
final int offset = 128;
return ByteCache.cache[(int)b + offset];
return (!PreviewFeatures.isEnabled()) ? ByteCache.cache[(int)b + offset] : new Byte(b);
}

/**
Expand Down
36 changes: 25 additions & 11 deletions src/java.base/share/classes/java/lang/Character.java
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Expand Up @@ -26,6 +26,7 @@
package java.lang;

import jdk.internal.misc.CDS;
import jdk.internal.misc.PreviewFeatures;
import jdk.internal.value.DeserializeConstructor;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import jdk.internal.vm.annotation.Stable;
Expand Down Expand Up @@ -9271,15 +9272,26 @@ private CharacterCache(){}
/**
* Returns a {@code Character} instance representing the specified
* {@code char} value.
* If a new {@code Character} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Character(char)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
*
* This method will always cache values in the range {@code
* '\u005Cu0000'} to {@code '\u005Cu007F'}, inclusive, and may
* cache other values outside of this range.
* <div class="preview-block">
* <div class="preview-comment">
* <p>
* - When preview features are NOT enabled, {@code Character} is an identity class.
* If a new {@code Character} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Character(char)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
* This method will always cache values in the range {@code
* '\u005Cu0000'} to {@code '\u005Cu007F'}, inclusive, and may
* cache other values outside of this range.
* </p>
* <p>
* - When preview features are enabled, {@code Character} is a {@linkplain Class#isValue value class}.
* The {@code valueOf} behavior is the same as invoking the constructor,
* whether cached or not.
* </p>
* </div>
* </div>
*
* @param c a char value.
* @return a {@code Character} instance representing {@code c}.
Expand All @@ -9288,8 +9300,10 @@ private CharacterCache(){}
@IntrinsicCandidate
@DeserializeConstructor
public static Character valueOf(char c) {
if (c <= 127) { // must cache
return CharacterCache.cache[(int)c];
if (!PreviewFeatures.isEnabled()) {
if (c <= 127) { // must cache
return CharacterCache.cache[(int) c];
}
}
return new Character(c);
}
Expand Down
35 changes: 25 additions & 10 deletions src/java.base/share/classes/java/lang/Integer.java
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Expand Up @@ -26,6 +26,7 @@
package java.lang;

import jdk.internal.misc.CDS;
import jdk.internal.misc.PreviewFeatures;
import jdk.internal.misc.VM;
import jdk.internal.util.DecimalDigits;
import jdk.internal.value.DeserializeConstructor;
Expand Down Expand Up @@ -996,14 +997,26 @@ private IntegerCache() {}

/**
* Returns an {@code Integer} instance representing the specified
* {@code int} value. If a new {@code Integer} instance is not
* required, this method should generally be used in preference to
* the constructor {@link #Integer(int)}, as this method is likely
* to yield significantly better space and time performance by
* caching frequently requested values.
*
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* {@code int} value.
* <div class="preview-block">
* <div class="preview-comment">
* <p>
* - When preview features are NOT enabled, {@code Integer} is an identity class.
* If a new {@code Integer} instance is not
* required, this method should generally be used in preference to
* the constructor {@link #Integer(int)}, as this method is likely
* to yield significantly better space and time performance by
* caching frequently requested values.
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* </p>
* <p>
* - When preview features are enabled, {@code Integer} is a {@linkplain Class#isValue value class}.
* The {@code valueOf} behavior is the same as invoking the constructor,
* whether cached or not.
* </p>
* </div>
* </div>
*
* @param i an {@code int} value.
* @return an {@code Integer} instance representing {@code i}.
Expand All @@ -1012,8 +1025,10 @@ private IntegerCache() {}
@IntrinsicCandidate
@DeserializeConstructor
public static Integer valueOf(int i) {
if (i >= IntegerCache.low && i <= IntegerCache.high)
return IntegerCache.cache[i + (-IntegerCache.low)];
if (!PreviewFeatures.isEnabled()) {
if (i >= IntegerCache.low && i <= IntegerCache.high)
return IntegerCache.cache[i + (-IntegerCache.low)];
}
return new Integer(i);
}

Expand Down
34 changes: 24 additions & 10 deletions src/java.base/share/classes/java/lang/Long.java
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Expand Up @@ -34,6 +34,7 @@
import java.util.Optional;

import jdk.internal.misc.CDS;
import jdk.internal.misc.PreviewFeatures;
import jdk.internal.value.DeserializeConstructor;
import jdk.internal.util.DecimalDigits;
import jdk.internal.vm.annotation.ForceInline;
Expand Down Expand Up @@ -989,14 +990,25 @@ private LongCache() {}
/**
* Returns a {@code Long} instance representing the specified
* {@code long} value.
* If a new {@code Long} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Long(long)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
*
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* <div class="preview-block">
* <div class="preview-comment">
* <p>
* - When preview features are NOT enabled, {@code Long} is an identity class.
* If a new {@code Long} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Long(long)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* </p>
* <p>
* - When preview features are enabled, {@code Long} is a {@linkplain Class#isValue value class}.
* The {@code valueOf} behavior is the same as invoking the constructor,
* whether cached or not.
* </p>
* </div>
* </div>
*
* @param l a long value.
* @return a {@code Long} instance representing {@code l}.
Expand All @@ -1006,8 +1018,10 @@ private LongCache() {}
@DeserializeConstructor
public static Long valueOf(long l) {
final int offset = 128;
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I recommend moving this into the preview feature block too.

if (l >= -128 && l <= 127) { // will cache
return LongCache.cache[(int)l + offset];
if (!PreviewFeatures.isEnabled()) {
if (l >= -128 && l <= 127) { // will cache
return LongCache.cache[(int) l + offset];
}
}
return new Long(l);
}
Expand Down
34 changes: 24 additions & 10 deletions src/java.base/share/classes/java/lang/Short.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
package java.lang;

import jdk.internal.misc.CDS;
import jdk.internal.misc.PreviewFeatures;
import jdk.internal.value.DeserializeConstructor;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import jdk.internal.vm.annotation.Stable;
Expand Down Expand Up @@ -269,14 +270,25 @@ private ShortCache() {}
/**
* Returns a {@code Short} instance representing the specified
* {@code short} value.
* If a new {@code Short} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Short(short)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
*
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* <div class="preview-block">
* <div class="preview-comment">
* <p>
* - When preview features are NOT enabled, {@code Short} is an identity class.
* If a new {@code Short} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Short(short)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
* </p>
* <p>
* - When preview features are enabled, {@code Short} is a {@linkplain Class#isValue value class}.
* The {@code valueOf} behavior is the same as invoking the constructor,
* whether cached or not.
* </p>
* </div>
* </div>
*
* @param s a short value.
* @return a {@code Short} instance representing {@code s}.
Expand All @@ -287,8 +299,10 @@ private ShortCache() {}
public static Short valueOf(short s) {
final int offset = 128;
int sAsInt = s;
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Same remark, I recommend moving this into the preview feature check block.

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I think you missed the sAsInt variable.

if (sAsInt >= -128 && sAsInt <= 127) { // must cache
return ShortCache.cache[sAsInt + offset];
if (!PreviewFeatures.isEnabled()) {
if (sAsInt >= -128 && sAsInt <= 127) { // must cache
return ShortCache.cache[sAsInt + offset];
}
}
return new Short(s);
}
Expand Down