'a'..'z'

[cruster]

Is it possible to achieve something like this?

switch (mystring.charAt(0)) {
case 'a'..'z':
// do something
break;
}

 

[Luc The Perverse]

Is it possible to achieve something like this?

switch (mystring.charAt(0)) {
case 'a'..'z':
// do something
break;
}

There are times when an if statement may be more appropriate

Sorry - java is not VB

 

[Bart Cremers]

cruster schreef:

Is it possible to achieve something like this?

switch (mystring.charAt(0)) {
case 'a'..'z':
// do something
break;
}

it's possible, only a bit ugly in Java:

switch (mystring.charAt(0)) {
case 'a':
case 'b':
....
case 'z:
// do something
break;
}

In this case you can of course go for an if test:

if (mystring.charAt(0) >= 'a' && mystring.charAt(0) <= 'z') {
// do something
}

Regards,

Bart

 

[bugbear]

There are times when an if statement may be more appropriate

Sorry - java is not VB

Or perl ;-)

BugBear

 

[Stefan Ram]

case 'a'..'z':

public class Main
{
public static void test( final char c )
{ switch( c >= 'a' && c <= 'z' ? -1 : c )
{ case -1: java.lang.System.out.println( "a .. z" ); break;
case '!': java.lang.System.out.println( "exclamation mark" ); break;
default: java.lang.System.out.println( "unknown" ); break; }}

public static void main( final java.lang.String[] args )
{ test( '\u0060' ); test( 'a' ); test( 'b' ); test( 'y' );
test( 'z' ); test( '{' ); test( '!' ); }}

 

[Chris Uppal]

Is it possible to achieve something like this?

switch (mystring.charAt(0)) {
case 'a'..'z':
// do something
break;
}

Yes. Easy:

switch (mystring.charAt(0))
{
case: 'a':
case: 'b':
case: 'c':
case: 'd':
case: 'e':
case: 'f':
case: 'g':
case: 'h':
case: 'i':
case: 'j':
case: 'k':
case: 'l':
case: 'm':
case: 'n':
case: 'o':
case: 'p':
case: 'q':
case: 'r':
case: 's':
case: 't':
case: 'u':
case: 'v':
case: 'w':
case: 'x':
case: 'y':
case: 'z': // do something
}

You may find

char c = mystring.charAt(0);
if (c >= 'a' && c <= 'z')
{
// do something
}

more expressive, though.

NB: if what you are really trying to do is characterise characters (identify
alphabetic characters, etc) then you'd almost certainly be better off
remembering that you are not working in ASCII but Unicode, and using the static
methods of class java.lang.Character, such as isLetter(int) and isLetter(char).

-- chris

 

[Jeffrey Schwab]

Is it possible to achieve something like this?

switch (mystring.charAt(0)) {
case 'a'..'z':
// do something
break;
}

You may want to write a method to categorize characters, and return an
integer constant or Enum to indicate the category of a given character.
E.g:

switch(categorize(myString.charAt(0)) {
case LOWERCASE_LETTER:
// do something
break;
// other cases...
}

 

[Chris Uppal]

Mark Space wrote:

[me:]

Oo, good point Something that's easy for C programmers to trip up
on...

Not to sound /too/ priggish, but even C programmers should know to use
isdigit() and so on in preference to hard-coding character classes.

;-)

-- chris

 

[Dale King]

There are times when an if statement may be more appropriate

And I don't think this is one of those cases! Switch statements should
support ranges and value lists. I submitted an RFE for such a feature
years ago:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4269827

Using a switch is more readable than the if-else and can actually be
much more efficient than if-else (see the comments I attached to the RFE).

 

[Luc The Perverse]

And I don't think this is one of those cases! Switch statements should
support ranges and value lists. I submitted an RFE for such a feature
years ago:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4269827

Using a switch is more readable than the if-else and can actually be much
more efficient than if-else (see the comments I attached to the RFE).

The listed example is basically an if statement. If there were even 1 or 2
other cases I would not have a problem with it.

 

[Dale King]

The listed example is basically an if statement. If there were even 1 or 2
other cases I would not have a problem with it.

I'm not sure what you mean by saying the example is basically an if
statement. The fact that it can only currently be expressed as an if
statement has no bearing on the matter.

Any switch statement can be recoded as a series of if statements. Yet
switch and if have different semantics.

The example I gave is a case where it is difficult to express the logic
using if statements in a way that is both readable and efficient.
Expanding cases to accept ranges and lists allow for a more readable
expression of the logic and the opportunity for the compiler to optimize
the comparisons.