黑马集合学习 自定义ArrayList01

 package demo;

 import java.util.Arrays;

 public class MyArrayList<T> {
     Object[] t;
     int size;
     private static final int MAX_ARRAY_SIZE = 5;
     private static final Object[] EMPTY_ELEMENTDATA = {};

     public MyArrayList(){
         //必须给t赋值，不然每次都必须判断t是否为null，影响效率
         t = EMPTY_ELEMENTDATA;
     }

     public boolean add(T e){
         //必须给t赋值，不然每次都必须在这里判断t是否为null，影响效率
         if(t.length == size){
             grow(size + 1);
         }
         t[size++] = e;
         return true;
     }

     private void grow(int minCapacity) {
         int newCapacity = t.length + t.length >> 1;
         //minCapacity溢出
         if(minCapacity < 0)
             throw new RuntimeException();
         //newCapacity < minCapacity必须加，因为刚开始时newCapacity增长小于minCapacity
         if(newCapacity < minCapacity || newCapacity < 0 || newCapacity > MAX_ARRAY_SIZE){
             if(minCapacity > MAX_ARRAY_SIZE){
                 throw new RuntimeException();
             }else{
                 //生长到最大
                 t = Arrays.copyOf(t, MAX_ARRAY_SIZE);
             }
         }else{
             //生长到newCapacity
             t = Arrays.copyOf(t, newCapacity);
         }
     }
 }

ArrayList一