ArrayList根据该
equals(Object obj)方法删除对象。因此，您应该正确实现此方法。就像是：
public boolean equals(Object obj) { if (obj == null) return false; if (obj == this) return true; if (!(obj instanceof ArrayTest)) return false; ArrayTest o = (ArrayTest) obj; return o.i == this.i;}要么
public boolean equals(Object obj) { if (obj instanceof ArrayTest) { ArrayTest o = (ArrayTest) obj; return o.i == this.i; } return false;}
