Android面试题之ArrayList源码详解

AntDreamer

于 2024-07-05 09:21:06 发布

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分类专栏： Android 文章标签： android java 面试性能优化数据结构

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ArrayList

public class ArrayList<E> extends AbstractList<E>
            implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
   
    /**
     * 默认ArrayList的容量为10
     */
    private static final int DEFAULT_CAPACITY = 10;

    /**
     * 可以看出ArrayList底层通过数组实现
     */
    private static final Object[] EMPTY_ELEMENTDATA = {
   };
    
    private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {
   };


    /**
     * 可以看出ArrayList基于数组实现
     */
    transient Object[] elementData;

    private int size;
    
    /**
     * 
     */
    public ArrayList() {
   
        this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
    }
    
    public ArrayList(int initialCapacity) {
   
        if (initialCapacity > 0) {
   
            this.elementData = new Object[initialCapacity];
        } else if (initialCapacity == 0) {
   
            this.elementData = EMPTY_ELEMENTDATA;
        } else {
   
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
        }
    }

    
     /**
     *获取大小
     */
    public int size() {
   
        return size;
    }

    /**
     *判断是否为空
     */
    public boolean isEmpty() {
   
        return size == 0;
    }
    
    public boolean contains(Object o