java compiler and string literals

[John and Diane Curley]

Hi, All:

Just verifying Java Compiler optimization and string literals. If I have
the following method, how many String objects are created in the for loop:

public void method() {
for(int i = 0; i < 1000000; i++) {
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
}
}

I say one object is created for the entire for loop and the code is fine, my
colleague says many and this code is inefficient. Any people want to
comment?

Thanks,
John

 

[Timo Stamm]

Hi, All:

Just verifying Java Compiler optimization and string literals. If I have
the following method, how many String objects are created in the for loop:

public void method() {
for(int i = 0; i < 1000000; i++) {
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
}
}

I say one object is created for the entire for loop and the code is fine, my
colleague says many and this code is inefficient. Any people want to
comment?

Only one String object is created. See $3.10.5 of the Java Language
Specification.


Timo

 

[java-interview]

only one String Object will be created

 

[java-interview]

only one String Object will be created

 

[Tony Morris]

Hi, All:

Just verifying Java Compiler optimization and string literals. If I have
the following method, how many String objects are created in the for loop:

public void method() {
for(int i = 0; i < 1000000; i++) {
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
}
}

I say one object is created for the entire for loop and the code is fine, my
colleague says many and this code is inefficient. Any people want to
comment?

Thanks,
John

None are create in the for loop. One is created at class load time from the
class' constant_pool.
See if this helps:
http://jqa.tmorris.net/GetQAndA.action?qids=68&showAnswers=true

 

[Chris Uppal]

[...] how many String objects are created in the for loop:

public void method() {
for(int i = 0; i < 1000000; i++) {
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
System.out.println("xxx");
}
}

I say one object is created for the entire for loop and the code is fine,
my colleague says many and this code is inefficient.

You and your collegue are both wrong, but he is a lot more wrong than you ;-)

/No/ strings are created in that loop. One instance of String ("xxx") is
created around about the time when the class is loaded. In the loop you refer
to that single pre-existing String five million times; you do not create any
strings at all.

-- chris