> On Jun 29, 2018, at 2:50 PM, Jonathan Gibbons <jonathan.gibb...@oracle.com>
> wrote:
>
> In that specific snippet, I would expect the compiler (javac) to fold the
> constants together.
>
Yes, and behold the use of indy string concat :-)
Classfile /Users/sandoz/Projects/jdk/jdk-test/target/classes/Test.class
Last modified Jun 29, 2018; size 873 bytes
MD5 checksum b6eb6030a1b0840263ecced5880a52e6
Compiled from "Test.java"
public class Test
SourceFile: "Test.java"
InnerClasses:
public static final #37= #36 of #40; //Lookup=class
java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles
BootstrapMethods:
0: #24 invokestatic
java/lang/invoke/StringConcatFactory.makeConcatWithConstants:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/invoke/CallSite;
Method arguments:
#25 bazbiz
minor version: 0
major version: 54
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
...
#22 = Utf8 barfoo
...
#25 = String #30 // bazbiz
{
public Test();
...
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=1, locals=2, args_size=1
0: ldc #2 // String barfoo
2: astore_1
3: aload_1
4: invokedynamic #3, 0 // InvokeDynamic
#0:makeConcatWithConstants:(Ljava/lang/String;)Ljava/lang/String;
9: astore_1
10: return
Paul.
> -- Jon
>
> On 06/29/2018 01:02 PM, Isaac Levy wrote:
>> Would this snippet end up merging two StringBuilders?
>>
>> String x = "bar" + "foo";
>> x += "baz" + "biz";
>>
>> I had trouble reading stringopts.cpp. I was thinking this append might
>> be common due to implicit StringBuilder creation.
>>
>> Isaac
>>
>>
>> On Fri, Jun 29, 2018 at 12:48 PM, Paul Sandoz <paul.san...@oracle.com> wrote:
>>> Hard to reconstruct the culture memory around this. I suspect such a new
>>> method was not considered necessary when StringBuilder was added to Java
>>> 1.5 given the CharSequence accepting method, and performance was not
>>> considered a concern, and I doubt it's a concern now.
>>>
>>> (I don’t think there is any circularity that would result from bridge
>>> methods if such a method was added.)
>>>
>>> Paul.
>>>
>>>> On Jun 27, 2018, at 10:22 PM, Martin Buchholz <marti...@google.com> wrote:
>>>>
>>>> I'm fairly sure the append(StringBuilder) overloads were left out
>>>> intentionally.
>>>>
>>>> On Wed, Jun 27, 2018 at 8:57 PM, Isaac Levy <isaac.r.l...@gmail.com> wrote:
>>>>
>>>>> AbstractStringBuilder already has append(<StringBuffer>). This patch
>>>>> adds append(<StringBuilder>).
>>>>>
>>>>> The new method improves parity between the two classes. In addition,
>>>>> combining StringBuilders is presumably common. append(<CharSequence>)
>>>>> has a couple insteadof checks, which this new method skips.
>>>>>
>>>>> -Isaac
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> diff --git a/src/java.base/share/classes/java/lang/
>>>>> AbstractStringBuilder.java
>>>>> b/src/java.base/share/classes/java/lang/AbstractStringBuilder.java
>>>>> index 2ef3e53256..1fe89bb92a 100644
>>>>> --- a/src/java.base/share/classes/java/lang/AbstractStringBuilder.java
>>>>> +++ b/src/java.base/share/classes/java/lang/AbstractStringBuilder.java
>>>>> @@ -543,6 +543,11 @@ abstract class AbstractStringBuilder implements
>>>>> Appendable, CharSequence {
>>>>> return this.append((AbstractStringBuilder)sb);
>>>>> }
>>>>>
>>>>> + // Documentation in subclasses because of synchro difference
>>>>> + public AbstractStringBuilder append(StringBuilder sb) {
>>>>> + return this.append((AbstractStringBuilder)sb);
>>>>> + }
>>>>> +
>>>>> /**
>>>>> * @since 1.8
>>>>> */
>>>>> diff --git a/src/java.base/share/classes/java/lang/StringBuffer.java
>>>>> b/src/java.base/share/classes/java/lang/StringBuffer.java
>>>>> index e597a8112e..613ba90c25 100644
>>>>> --- a/src/java.base/share/classes/java/lang/StringBuffer.java
>>>>> +++ b/src/java.base/share/classes/java/lang/StringBuffer.java
>>>>> @@ -313,6 +313,33 @@ import jdk.internal.HotSpotIntrinsicCandidate;
>>>>> return this;
>>>>> }
>>>>>
>>>>> + /**
>>>>> + * Appends the specified {@code StringBuilder} to this sequence.
>>>>> + * <p>
>>>>> + * The characters of the {@code StringBuilder} argument are appended,
>>>>> + * in order, to the contents of this {@code StringBuffer}, increasing
>>>>> the
>>>>> + * length of this {@code StringBuffer} by the length of the argument.
>>>>> + * If {@code sb} is {@code null}, then the four characters
>>>>> + * {@code "null"} are appended to this {@code StringBuffer}.
>>>>> + * <p>
>>>>> + * Let <i>n</i> be the length of the old character sequence, the one
>>>>> + * contained in the {@code StringBuffer} just prior to execution of
>>>>> the
>>>>> + * {@code append} method. Then the character at index <i>k</i> in
>>>>> + * the new character sequence is equal to the character at index
>>>>> <i>k</i>
>>>>> + * in the old character sequence, if <i>k</i> is less than <i>n</i>;
>>>>> + * otherwise, it is equal to the character at index <i>k-n</i> in the
>>>>> + * argument {@code sb}.
>>>>> + * <p>
>>>>> + *
>>>>> + * @param sb the {@code StringBuilder} to append.
>>>>> + * @return a reference to this object.
>>>>> + */
>>>>> + public synchronized StringBuffer append(StringBuilder sb) {
>>>>> + toStringCache = null;
>>>>> + super.append(sb);
>>>>> + return this;
>>>>> + }
>>>>> +
>>>>> /**
>>>>> * Appends the specified {@code StringBuffer} to this sequence.
>>>>> * <p>
>>>>> diff --git a/src/java.base/share/classes/java/lang/StringBuilder.java
>>>>> b/src/java.base/share/classes/java/lang/StringBuilder.java
>>>>> index 40da2083c2..5ddd4fb5f9 100644
>>>>> --- a/src/java.base/share/classes/java/lang/StringBuilder.java
>>>>> +++ b/src/java.base/share/classes/java/lang/StringBuilder.java
>>>>> @@ -199,6 +199,30 @@ public final class StringBuilder
>>>>> return this;
>>>>> }
>>>>>
>>>>> + /**
>>>>> + * Appends the specified {@code StringBuilder} to this sequence.
>>>>> + * <p>
>>>>> + * The characters of the {@code StringBuilder} argument are appended,
>>>>> + * in order, to this sequence, increasing the
>>>>> + * length of this sequence by the length of the argument.
>>>>> + * If {@code sb} is {@code null}, then the four characters
>>>>> + * {@code "null"} are appended to this sequence.
>>>>> + * <p>
>>>>> + * Let <i>n</i> be the length of this character sequence just prior
>>>>> to
>>>>> + * execution of the {@code append} method. Then the character at
>>>>> index
>>>>> + * <i>k</i> in the new character sequence is equal to the character
>>>>> at
>>>>> + * index <i>k</i> in the old character sequence, if <i>k</i> is less
>>>>> than
>>>>> + * <i>n</i>; otherwise, it is equal to the character at index
>>>>> <i>k-n</i>
>>>>> + * in the argument {@code sb}.
>>>>> + *
>>>>> + * @param sb the {@code StringBuilder} to append.
>>>>> + * @return a reference to this object.
>>>>> + */
>>>>> + public StringBuilder append(StringBuilder sb) {
>>>>> + super.append(sb);
>>>>> + return this;
>>>>> + }
>>>>> +
>>>>> @Override
>>>>> public StringBuilder append(CharSequence s) {
>>>>> super.append(s);
>>>>>
>
