Integer 为空赋值给int

public static void main(String[] args) throws Exception {
Integer i = null;
test(i);
System.out.print(i);
}

public static void test(int i){
System.out.print(i);
int n = 0;
n = i;
System.out.print(n);
}

public static void main(String[] arg){
int i = 0;
test(i);

Map<Long,Integer> map = new HashMap<Long,Integer>();
map.put((long) 1, null);

test2(map.get(1));
}
public static void test(Integer id){
System.out.print("+++++++++++++++++" +   id);
}

public static void test2(Integer id){
int i = id;
System.out.print(id);
}