ArrayList 基于 equals(Object obj) 方法移除对象.所以你应该正确地实施这个方法.类似的东西:

ArrayList removes objects based on the equals(Object obj) method. So you should implement properly this method. Something like:

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;
}

或

public boolean equals(Object obj) {
    if (obj instanceof ArrayTest) {
        ArrayTest o = (ArrayTest) obj;
        return o.i == this.i;
    }
    return false;
}