Re: Making a char a CharSequence.

Hakusa@gmail.com wrote:


After several attempts, I think I see what you mean.

There exists a String.contains(CharSequence) method, but no
String.contains(char). How does one go about achieving the equivalent of
the fictional method...?

The direct answer is that you can create a CharSequence with a single
char, using Character.toString(char). Or you could create a compact
implementation if you really had to (performance, memory, whatever)
(code below).

The simpler way is do what we did before 1.5: Use String.indexOf != -1.

BTW: It's less confusing if you stick to code conventions.

Tom Hawtin

public final class SingletonCharSequence implements CharSequence {
     private final char c;
     public SingletonCharSequence(char c) {
         this.c = c;
     }
     public char charAt(int index) {
         if (index != 0) {
             throw new IndexOutOfBoundsException();
         }
         return c;
     }
     public int length() {
         return 1;
     }
     public CharSequence subSequence(int start, int end) {
         if (start == end) {
             if (start == 0 || start == 1) {
                 return "";
             } else {
                 throw new IndexOutOfBoundsException();
             }
         } else if (start == 0 && end == 1) {
             return this;
         } else {
             throw new IndexOutOfBoundsException();
         }
     }
     @Override
     public String toString() {
         return Character.toString(c);
     }
     // Nice to have method (a.k.a. premature generalisation...)
     @Override
     public int hashCode() {
         return c;
     }
     @Override
     public boolean equals(Object obj) {
         if (!(obj instanceof SingletonCharSequence) {
             return false;
         }
         SingletonCharSequence other = (SingletonCharSequence)obj;
         return this.c == other.c;
     }
}
(Usual disclaimer...)