Java Java.util.ArrayList.add()用法及代码示例

以下是Java中ArrayList的add()方法：

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

   参数:    
   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<Integer> arrlist = new ArrayList<Integer>(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元素)：此方法将指定的元素E插入此列表中的指定位置。它将当前在该位置的元素(如果有)和任何后续元素向右移动(将向其索引添加一个)。

   参数:
   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<Integer> arrlist = new ArrayList<Integer>(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