How to use Java ArrayList

ArrayList is the list class of Java, in the project development is very common, then how to add, delete, modify, query, traverse ArrayList? This article will be elaborated in detail.

Tools/Materials

• Java

First, the method of adding ArrayList

2. 1

   Method 1: Add data to the ArrayList sequentially in sequence.

   Usage:

   Add A to List

   List.add ("a");

   #例子:

4. 2

   Method 2: Add a second data after the nth data

   Usage:

   Add an E after the 1th element

   List.add (1, "E");

   Note: There must be enough data in the ArrayList, such as there is no data in the ArrayList, this time using Arraylist.add (1, "E"), there will be a java.lang.IndexOutOfBoundsException exception.

   #例子:

6. 3

   Method 3: Add all the data from one ArrayList to another arralist

   Usage:

   Add all data from List2 to List1

   List1.addall (LIST2);

   #例子:

8. 4

   Method 4: Add all the data from one ArrayList to the nth element in the other arralist.

   Usage:

   Adds all the data from List2 to the 2nd element in List1.

   List1.addall (2,LIST2);

   #例子:

   END

Second, the deletion method of ArrayList

2. 1

   Method 1: Delete individual data by location

   Usage:

   Delete the 2nd data in the list

   List.remove (2);

   Note: the position is calculated starting from 0 (0, 1, 2, 3 ...)

   #例子

4. 2

   Method 2: Delete individual data by content

   Usage:

   Remove the data "D" from the list

   List.remove ("D");

   Note: raw type data such as Int,string,char can be deleted, but for complex objects, such as the user class and the person class object that you write, you need to override the Equals method, which is responsible for removing the Remove method.

   #例子

6. 3

   Method 3: Delete multiple data at the same time as the collection

   Usage:

   Follow the data in List2 to remove List1

   List.removeall (LIST2);

   #例子

8. 4

   Method 4: Empty the ArrayList

   Usage:

   Clear List

   List.clear ();

   #例子

   END

Three, the modification method of ArrayList

1. 1

   Method 1: Modify the element at the specified location

   Usage:

   Change the 2nd element in the list to M

   List.set (2, "M");

   Note: the position is calculated starting from 0 (0, 1, 2, 3 ...)

   #例子

   END

Iv. Query of ArrayList

1. Method 1: get the specified position element

   Usage:

   Gets the 2nd element in the list

   String ele = List.get (2);

   Note: the position is calculated starting from 0 (0, 1, 2, 3 ...)

   #例子

How to use Java ArrayList