Java ArrayList构造分析

 1 /** 
 2       * The array buffer into which the elements of the ArrayList are stored. 
 3       * The capacity of the ArrayList is the length of this array buffer. 
 4       */  
 5      private transient Object[] elementData;  
 6    
 7      /** 
 8       * The size of the ArrayList (the number of elements it contains). 
 9       * 
10       * @serial 
11       */  
12      private int size;  

1 public boolean add(E e) {  
2     ensureCapacity(size + 1);  // Increments modCount!!  
3     elementData[size++] = e;  
4     return true;  
5 }  

/** 
      * Increases the capacity of this <tt>ArrayList</tt> instance, if 
      * necessary, to ensure that it can hold at least the number of elements 
      * specified by the minimum capacity argument. 
      * 
      * @param   minCapacity   the desired minimum capacity 
      */  
     public void ensureCapacity(int minCapacity) {  
     modCount++;  
     int oldCapacity = elementData.length;  
     if (minCapacity > oldCapacity) {  
         Object oldData[] = elementData;  
         int newCapacity = (oldCapacity * 3)/2 + 1;  
             if (newCapacity < minCapacity)  
         newCapacity = minCapacity;  
             // minCapacity is usually close to size, so this is a win:  
             elementData = Arrays.copyOf(elementData, newCapacity);  
     }  
     }