RE: String/StringBuffer (was Re: An alternative to JSP)
Paul,
Actually, my investigations in the past have shown that (at least in
Sun's JDK 1.2) this is implemented as:
new StringBuffer
("My").append("dog").append("has").append("fleas").toString();
It is also possible to write a statement like:
"My" + "dog" + '.'
The ability to concatenate a char points at an underlying StringBuffer
implementation, which supports append(String) and
append(char) methods.
Last paragraph in the java.lang.String javadoc says:
The Java language provides special support for the string
concatentation operator
( + ), and for conversion of other objects to strings. String
concatenation is
implemented through the StringBuffer class and its append
method. String
conversions are implemented through the method toString,
defined by Object and
inherited by all classes in Java. For additional information
on string concatenation
and conversion, see Gosling, Joy, and Steele, The Java
Language Specification.
On a performance note, doesn't it strike anybody the methods
on StringBuffer are declared 'synchronized' is a bad thing?
Object creation and synchronization are 2 of the most costly operations in
Java.
- Chris.
Brainbench MVP Java2.
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RE: String/StringBuffer (was Re: An alternative to JSP)
Last paragraph in the java.lang.String javadoc says:
The Java language provides special support for the string
concatentation operator
( + ), and for conversion of other objects to strings. String
concatenation is
implemented through the StringBuffer class and its append
method. String
conversions are implemented through the method toString,
defined by Object and
inherited by all classes in Java. For additional information
on string concatenation
and conversion, see Gosling, Joy, and Steele, The Java
Language Specification.
And the Java Language Specification (Section 3.10.5: String Literals) says
this:
"Strings computed by constant expressions (15.27) are computed at compile
time and then treated as if they were literals"
http://java.sun.com/docs/books/jls/html/3.doc.html#101083
Just thought that I would point out that:
"My " + "dog " + "has " + "fleas." will be compiled as one String:
"My dog has fleas." and incurs no runtime penalties. In the case
Paul,
Actually, my investigations in the past have shown that (at least in
Sun's JDK 1.2) this is implemented as:
new StringBuffer
("My").append("dog").append("has").append("fleas").toString();
If this is actually the case, Sun's JDK is not in compliance with the spec.
However, in my tests, this is not the case.
From this class:
public class StringTest {
static String blah = "My " + "dog " + "has " + "fleas.";
}
The following is the result from "javap -c StringTest" after compiling:
Compiled from StringTest.java
public class StringTest extends java.lang.Object {
static java.lang.String blah;
static {};
public StringTest();
}
Method static {}
0 ldc #1 String "My dog has fleas."
2 putstatic #5 Field java.lang.String blah
5 return
Method StringTest()
0 aload_0
1 invokespecial #4 Method java.lang.Object()
4 return
regards,
michael
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RE: String/StringBuffer (was Re: An alternative to JSP)
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Subject: RE: String/StringBuffer (was Re: An alternative to JSP)
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Last paragraph in the java.lang.String javadoc says:
The Java language provides special support for the string
concatentation operator
( + ), and for conversion of other objects to strings. String
concatenation is
implemented through the StringBuffer class and its append
method. String
conversions are implemented through the method toString,
defined by Object and
inherited by all classes in Java. For additional information
on string concatenation
and conversion, see Gosling, Joy, and Steele, The Java
Language Specification.
And the Java Language Specification (Section 3.10.5: String Literals) says
this:
"Strings computed by constant expressions (15.27) are computed at compile
time and then treated as if they were literals"
http://java.sun.com/docs/books/jls/html/3.doc.html#101083
Just thought that I would point out that:
"My " + "dog " + "has " + "fleas." will be compiled as one String:
"My dog has fleas." and incurs no runtime penalties. In the case
Paul,
Actually, my investigations in the past have shown that (at least in
Sun's JDK 1.2) this is implemented as:
new StringBuffer
("My").append("dog").append("has").append("fleas").toString();
If this is actually the case, Sun's JDK is not in compliance with the spec.
However, in my tests, this is not the case.
From this class:
public class StringTest {
static String blah = "My " + "dog " + "has " + "fleas.";
}
The following is the result from "javap -c StringTest" after compiling:
Compiled from StringTest.java
public class StringTest extends java.lang.Object {
static java.lang.String blah;
static {};
public StringTest();
}
Method static {}
0 ldc #1 String "My dog has fleas."
2 putstatic #5 Field java.lang.String blah
5 return
Method StringTest()
0 aload_0
1 invokespecial #4 Method java.lang.Object()
4 return
Michael,
thanks. I stand corrected.
Arieh
regards,
michael
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