如何检查角色是否正确

Question

I have a bunch of characters and want to remove everything that isn't a '#' '.' 'E' and 'G'.

I tried to use this:

if (buffer.get(buffertest) == 'G'|'E'|'#'|'.')

But got an issue with an incompatible type.

Answer 1

This root problem is incorrect use of the bitwise OR operator, and the Java operator precedence hierarchy. Java expressions of this type are evaluated left to right, and the == operator takes precedence over |. Which when combined, your expression roughly translates to:

(buffer.get(buffertest) == 'G') | 'E' | '#' | '.'

The first part of the expression buffer.get(buffertest) == 'G' evaluates to a boolean.<br> The second part of the expression 'E' | '#' | '.'` evaluates to an int, which is narrowed to a char

Which leads to an incompatible type compile time error. You can correct your code by expanding the check this way:

char ch = buffer.get(buffertest);
if(ch == 'G' || ch == 'E' || ch == '#' || ch == '.') {
   // do something
}

Answer 2

You haven't shown the type of buffer , which makes things harder. But assuming buffer.get returns a char , you could use:

if ("GE#.".indexOf(buffer.get(buffertest) >= 0)

Or you could check each option explicitly, as per Simulant's answer... or to do the same thing but only calling get once:

char x = buffer.get(buffertest);
if (x == 'G' || x == 'E' || x == '#' || x == '.')

Your original code is failing because | is trying to perform a bitwise "OR" operation on the four characters... it's not the same thing as performing a logical "OR" on four conditions .

Answer 3

You need to compare for each character individually. Assuming that buffer.get(buffertest) returns a char , here's how to do it:

char c = buffer.get(buffertest);
if (c == 'G' || c == 'E' || c == '#' || c == '.') {
    // do something
}

Alternatively, you could do something like this:

char c = buffer.get(buffertest);
if ("GE#.".contains(Character.toString(c))) {
    // do something
}

Answer 4

if (buffer.get(buffertest) == 'G'||
 buffer.get(buffertest) == 'E'||
 buffer.get(buffertest) == '#'||
 buffer.get(buffertest) == '.')