First pattern i learned:

how to avoid an else:

value = else-value ;
if ( ... ) value = conditional-value;

-------

method returns null or good object. reduce code:

	public String getMethodNameForOperator(String op) {
		String name = aliases.get(op);
		if ( name==null ) {
			Tool.error("no such operator for "+name+": "+op);
		}
		return name;
	}

---------
class org

class T ... {
	const
	static fields
	fields	
	ctors
	methods
	util, support
	toString()
}

------------
if ( cond ) return true;
else return false;
->
return cond;
-----------
exchange values

				List tmp = pong;
				pong = ping;
				ping = tmp;