Object-Oriented Techniques - Java - page 311

single value (in this case, return the offset in the return statement, and let the user know that
-1 indicates not found), or define a trivial wrapper class containing both the integer and the
Boolean. However, there is precedent in the standard API: this code is remarkably similar to
how the ParsePosition class is used. Anyway, this functionality is requested often enough
that I feel justified in showing how to do it, accompanied by this disclaimer: try to avoid do-
ing it this way in new code!

Having said all that, here is the MutableInteger class:

com/darwinsys/lang/MutableInteger.java

package package com . darwinsys . lang ;

/** A MutableInteger is like an Integer but mutable, to avoid the
* excess object creation involved in
* c = new Integer(c.getInt()+1)
* which can get expensive if done a lot.
* Not subclassed from Integer, since Integer is final (for performance :-))
*/
public public class class MutableInteger MutableInteger {

private private int int value = 0 ;

public public MutableInteger ( int int i ) {

value = i ;

}

public public MutableInteger () {

this

this ( 0 );

}

public public int int incr () {

value ++;
return return value ;

}

public public int int amt ) {

value += amt ;
return

int incr ( int

return value ;

}

public public int int decr () {

value --;
return return value ;

}