java内存地址

public static void main(String[] args) {
OrderItem oi
= new OrderItem();
oi.setId(1L);
System.out.println(oi.getId());
OrderItem oi1 = a(oi);
System.out.println(oi.getId());
b(oi);
System.out.println(oi.getId());
int i = 300;
System.out.println(i);
c(i);
System.out.println(i);
d(i);
System.out.println(i);
Integer j = 100;
System.out.println(j);
e(j);
System.out.println(j);
f(j);
System.out.println(j);
c(j);
System.out.println(j);
d(j);
System.out.println(j);
}

public static Integer e(Integer integer){
integer = 400;
return integer;
}
public static Integer f(Integer integer){
integer = 500;
return integer;
}

public static int c(int n){
n = 300;
return n;
}

public static int d(int n){
n = 400;
return n;
}
public static OrderItem a(OrderItem oi){
oi = new OrderItem();
oi.setId(2L);
return oi;
}
public static OrderItem b(OrderItem oi){
oi.setId(3L);
return oi;
}