void intersection(Menge a) {  
		int j = 0;
		int[] tmp;
		if(this.elements.length >= a.elements.length){
			tmp = new int[this.elements.length];
			
			for (int i = 0; i < this.elements.length; i++) {
				if(isElement(a.elements[i])) {
					tmp[i] = a.elements[i];
					j++;
				}
			}
		} else {
			tmp = new int[a.elements.length];
			for (int i = 0; i < a.elements.length; i++) {
				if(isElement(a.elements[i])) {
					tmp[i] = a.elements[i];
					j++;
				}
			}
			
		}
		int[] tmp1 = new int[j];
		
			for (int k = 0; k < j; k++) {
				tmp1[k] = tmp[k];
			}
		this.elements = tmp1;
		
	}