The ArrayList of the Core Java thing.

The ArrayList of the Core Java thing.

　　High-rise ground, Java Foundation to pick up. Today, I looked at the core Java from the basic point to find a little bit to share.

First of all, the professional-level Lucky Star actor---employee Class (PS: I am focused on Lucky Star 30), there will be several appearances, so first here to introduce:

1 class employee{2   Private String name; 3   Private Double salary; 4   Private int ID; 5 6   // here is the set, get  method 7 }

ArrayList

First of all, please ArrayList debut and introduce yourself: I am a generic class (generic class) that takes a type parameter (types parameter). To specify the element object type that the array list holds, I use a pair of angle brackets to enclose the class name, such as,arraylist<employee> (Employee: It's my turn to Lucky Star) ... Balabala (omit 10086 words here). Well, here's how to use him.

　　1. Disclaimer:

1 New Arraylist<employee> ();

　　God, there are employee on both sides, which is too much trouble. If you have trouble, please use Java7, in Java7, you can omit the right type parameter as follows:

1 New Arraylist<> ();

　　This is also referred to as the "diamond" syntax, because an empty angle bracket is like a diamond. You can use the diamond syntax in conjunction with the new operator. The compiler checks what the new value is, if it is assigned to a variable, or is passed to a method, or is returned from a method, the compiler examines the generic type of the variable, parameter, or method, and then places the type in <>, in this case, the Lucky Star actor is the employee, Therefore, the generic type is employee.

　　2. Add :

1 staff.add (new Employee ("Harry Hacker" ...)); 2 staff.add (new Employee ("Tony Michel" ...));

3. Get the actual size of the array:

1 staff.size ();

　　4. Accessing array list elements :

　　4.1. Replace:

1 staff.set (I,harry);

Note: This method is somewhat equivalent to A[i]=harry. However, this method can only replace the element content that already exists in the array.

　　4.2. Get :

1 Employee e = Staff.get (i);

　Equivalent to: Employee e = a[i];

　　5. Insert the new element :

1 New Arraylist<>(); 2  while (...) 3 {4    x= ...; 5    List.add (x);   6 }

View Code

you can then use the ToArray method to copy the array into an array.

1 New x[list.size ()]; 2 List.toarray (a);

In addition, you can include elements in the middle of the array list:

1 int n = staff.size ()/2; 2 staff.add (n, e);

6. Delete the element :

1 Employee e = Staff.remove (n);

7. Iterate through the array :

　　General Method :

1  for (int i = 0; I<staff.size (); i++) 2 {3     Employee e = staff.get (i); 4     // Do somne thing with e 5  }

a method of forcing a little higher (for Each loop):

1  for (Empolyee e:staff) 2 {3     // Do something withe e 4  }

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The ArrayList of the Core Java thing.