compile error

someone please tell me what's wrong with my code
i keep getting this error message.

code is:
class SortAString { public static void main(String args[]) { String s=args[0]; int t=s.length(); for(int i=0;i<t-1;i++) { for(int j=i+1;i<t;i++) { char x=s.charAt(i); char y=s.charAt(j); if(x>y) { char tmp=x; x=y; y=tmp; } s.charAt(i)=x; s.charAt(j)=y; } } System.out.println(s); } }
error is:
unexpected type
required: variable
found: value

Welcome to the Ranch!

Please use code tags when posting you code.

The problem is here:

s.charAt(i)=x; s.charAt(j)=y;

You are trying to assign to a substring. This is a natural thing to assume you can do, but strings in Java are immutable, so you need to create a new string. Probably you need substring() or StringBuilder.

It's nothing to do with the immutability of Strings. Method calls cannot be used on the left hand side of an assignment expression.

Joanne Neal wrote:It's nothing to do with the immutability of Strings. Method calls cannot be used on the left hand side of an assignment expression.

Okay, but why can't you have an expression on the LHS? In Perl and some BASICs you can do this:

my $s = "tank"; substr($s, 0, 1) = "s"; #$s is now "sank"

Perl allows this because in Perl, strings are mutable. The reason Java doesn't is because strings are immutable.

Knute Snortum wrote:Perl allows this because in Perl, strings are mutable. The reason Java doesn't is because strings are immutable.

I don't know how it works in Perl, but Joanne is right. It's nothing to do with the immutability of Strings.
In Java you just can not have a method call on the left side of an assignment operator.

Hi, Welcome to the Ranch!

As Knute advised, it is best to UseCodeTags (<- click link) when posting nicely indented code. Apart from it looking nice, it makes it much easier to read which in turn improves your chances of getting a good reply to your questions. I've added them for you this time, looks much better don't you think?

Regards, Tim

Knute Snortum wrote:The reason Java doesn't is because strings are immutable.

StringBuilders in java are mutable, but this code won't compile
StringBuilder sb = new StringBuilder("heglo"); sb.charAt(2) = 'l';