Исходный файл Substitution.java:

class Substitution {
    static final int MAX_SIZE = 1024;
    int siz;
    int num[];

    public Substitution() {
        siz = 0;
        num = new int[MAX_SIZE-1];    
    }
    

    public Substitution(int size, int numbers[]) {
        siz = size;
        int i,j;
        num = new int[MAX_SIZE-1];
	int newSize = java.lang.reflect.Array.getLength(numbers);
	boolean isOk = true;

	for(i=0; i < newSize; i++)
	    for(j=i + 1; j < newSize; j++)
		if((numbers[i] == numbers[j]) || (numbers[i] > size) || (numbers[i] < 1)) 
		    isOk = false;

	if(isOk)
            for (i=0; i < newSize; i++)
                num[i] = numbers[i];
	else
	    System.out.println("This is not a substitution!");
    } 
    

    public int size() { return siz; }        
   

    public int map(int i) { return num[i]; }
 

    public Substitution multiply (Substitution s) {
	if(siz != s.size()) {
	    System.out.println("They are of different size!");
	    return new Substitution();
	} else {
	    int newNumbers[] = new int[siz];
	    int i;

	    for(i=1; i <= siz; i++)
		newNumbers[i-1] = s.map(num[i-1]-1);
	    return new Substitution(siz, newNumbers);
	}
    }

    public Substitution inverse() {
	int newNumbers[] = new int[siz];
	int i,j;

	for(i=1; i <= siz; i++)
	    for(j=1; j <= siz; j++)
		if(num[j-1] == i)
		    newNumbers[i-1] = j;

	return new Substitution(siz, newNumbers);
    }
}