Java方法参数的使用情况

public static void tripleValue(double x){
x = 3 * x;
}

double percent = 10;
tripleValue(percent);
//the value of percent still be 10

public static void tripleSalary(Employee x){
x.raiseSalary(200);
}

harry = new Employee(...);
tripleSalary(harry);

public static void swap(Employee x, Employee y){
Employee temp = x;
y = temp;
}

Employee a = new Employee("Alice",...);
Employee b = new Employee("Bob",...);
swap(a, b);
// dose a now refer to Bob, b to Alice?
//in fact a still refer to Alice, b still refer to Bob.