2018-12-20

1.ArrayList源码

ArrayList 有一个初始化的容量是10 MIN_CAPACITY_INCREMENT =10
add方法源码

object[] a = array;
int s = size;
if (s == a.length){
  object[] newArray = new Object[ s+
      (s < MIN_CAPACITY_INCREMENT / 2) ?  MIN_CAPACITY_INCREMENT :s >> 1)];
} 
System.arraycopy(a,0,newArray,0,s);
a[s] = object;
size = newSize;

解释：当长度等于数组长度的时候 开始扩容