牛客网java一面凉经
第一题:
hashCode() equals(Object o)
附带:volatile的具体作用,可见性你怎么理解,然后又给了代码,问问volatile能不能删除
public class Singleton { private volatile static Singleton instance = null; private Singleton(){ } public static Singleton getInstance(){ if(instance == null){ synchronized (Singleton.class) { if(instance == null){ instance = new Singleton(); } } } return instance; } }
第二题:
mysql
表user
id
name
age
表user_test
user_id
score
class_name
找出score 位于60~69的学生姓名,成绩和课程名,按照成绩降序排列
附带问了:join,索引, 主键索引和普通索引的区别,事务隔离性怎么理解
3 LInux操作
a.log
time ip msg
想统计出每一个ip出现的次数,按照次数降序排列
如何查看当前机器的tcp连接情况 4手撕代码英文题
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,
"A man, a plan, a canal: Panama"is a palindrome.
"race a car"is not a palindrome.
Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.
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