public class RecursionException extends RuntimeException {
public Object arg;
public RecursionException(Object arg) {
this.arg = arg;
}
public Object getArgs() {
return arg;
}
}
public abstract class Recursion<T> {
private final int maxStackDepth;
private int stackDepth = 0;
public Recursion(int maxStackDepth) {
this.maxStackDepth = maxStackDepth;
}
public abstract T run(Object arg) throws RecursionException;
public void increaseDepth(Object arg) {
stackDepth++;
if (stackDepth == maxStackDepth) {
stackDepth = 0;
throw new RecursionException(arg);
}
}
public T call(Object arg) {
Object currentArg = arg;
while (true) {
try {
return run(currentArg);
} catch (RecursionException ex) {
System.out.println("catched!"); //nur zu Testzwecken
currentArg = ex.getArgs();
}
}
}
}
public class RecursionTest {
public static void main(String... args) {
System.out.println(addUp(1000,0));
//System.out.println(addUp(100000,0)); --> StackoverflowException
//der analoge Aufruf:
Recursion<Long> rec = new Recursion<Long>(1000) {
@Override
public Long run(Object arg) throws RecursionException {
increaseDepth(arg);
long[] data = (long[]) arg;
if (data[0] == 0) return data[1];
return run(new long[]{data[0]-1,data[0]+data[1]});
}
};
System.out.println(rec.call(new long[]{100000, 0}));
}
private static long addUp(int i, long sum) {
if (i == 0) return sum;
return addUp(i-1, sum + i);
}
}
