Java Java () 方法

下面是Java中ArrayList的 add() 方法：

1. boolean add(Object o) ：此方法将指定元素附加到此列表的末尾。

   Parameters:    
   object o: The element to be appended to this list.
   Exception: NA

   // Java code to illustrate add(Object o)
   import java.io.*;
   import java.util.ArrayList;
     
   public class ArrayListDemo {
   public static void main(String[] args)
       {
     
           // create an empty array list with an initial capacity
           ArrayList arrlist = new ArrayList(5);
     
           // use add() method to add elements in the list
           arrlist.add(15);
           arrlist.add(20);
           arrlist.add(25);
     
           // prints all the elements available in list
           for (Integer number : arrlist) {
               System.out.println("Number = " + number);
           }
       }
   }
   

   输出：

   Number = 15
   Number = 20
   Number = 25
   

2. void add(int index, Object element) ：此方法在此列表中的指定位置插入指定元素 E。它将当前位于该位置的元素（如果有）和任何后续元素向右移动（将在其上添加一个指数）。

   Parameters:
   index : The index at which the specified element is to be inserted.
   element : The element to be inserted.
   
   Exception:
   Throws IndexOutOfBoundsException if the specified
   index is out of range (index  size()).

   // Java code to illustrate
   // void add(int index, Object element)
   import java.io.*;
   import java.util.ArrayList;
     
   public class ArrayListDemo {
   public static void main(String[] args)
       {
     
           // create an empty array list with an initial capacity
           ArrayList arrlist = new ArrayList(5);
     
           // use add() method to add elements in the list
           arrlist.add(10);
           arrlist.add(22);
           arrlist.add(30);
           arrlist.add(40);
     
           // adding element 35 at fourth position
           arrlist.add(3, 35);
     
           // let us print all the elements available in list
           for (Integer number : arrlist) {
               System.out.println("Number = " + number);
           }
       }
   }
   

   输出：

   Number = 10
   Number = 22
   Number = 30
   Number = 35
   Number = 40