static

static存在的时候，调用b2.setN(5)，sum=6，去掉static，sum从0开始

class B{
	int n;
	static int sum= 0;  
	void setN(int n){
		this.n= n;
		System.out.println("this.n= "+ this.n);
	}
	int getSum(){
		for(int i= 1;i<= n; i++){
			sum= sum+ i;
		}
		System.out.println(sum);
		return sum;
	}
	
}

public class Example4_9 {
	public static void main(String[] args) {
		B b1=new B(), b2= new B();
		b1.setN(3);
		b2.setN(5);
		int a1= b1.getSum();
		int a2= b2.getSum();
		System.out.println(a1+ a2);
	}
}