我已经坐了 2 个小时了,我找不到解决方案。我无法将多个朋友添加到我的 ArrayList,因为如果手机为空,它会从我的 getFriend()
方法中强制转换异常,而不是将其添加到列表中。解决此问题的简单方法是什么?
/**
* Ensures you can only add a friend if a friend with same phone number doesn't exist
* @param f as Friend
* @return boolean
*/
public boolean addFriend(Friend f){
if(getFriend(f.getPhone()) == null) {
friends.add(f);
return true;
}
else {
System.out.println("-------------------------------------");
System.out.println("Member with that phone already exists");
System.out.println("-------------------------------------");
return false;
}
}
/**
* Searches the arraylist for a friend matching phone
*
* @param phone as String
* @return Friend if matching phone, else returns a null
*/
public Friend getFriend(String phone) {
Friend res = null;
if(friends.size() != 0){
for(Friend f : friends) {
if(f.getPhone().equals(phone)){
res = f;
}
}
if(res == null){
throw new NullPointerException("No result found");
}
}
return res;
}
更改
if(res == null){
throw new NullPointerException("No result found");
}
简单地返回null
.
当您检查null
时,它将是安全的。
public Friend getFriend(String phone) {
if(friends.size() != 0){
for(Friend f : friends) {
if(f.getPhone().equals(phone)){
return f;
}
}
}
return null;
}
if(res == null && friends.size() == 0){
怎么样?这是一个有效的解决方案吗?