记百度面试

记百度面试_20211115

根据回忆，还原了下面试题

视频面试，很直接，直接上题

题1：JVM

从类加载讲起

import java.lang.reflect.Constructor;

public class Test {

    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException {
        Student student1 = new Student();
        student1.setName("张三");
        Student student2 = new Student();
        student2.setName("张三");

        student1 = null;

        System.gc();

        Class<Student> clazz = (Class<Student>) Class.forName("Test.Student");
        Constructor<Student> constructor = clazz.getConstructor(String.class);
    }

    static class Student {
        private String name;

        public Student() {
        }

        public Student(String name) {
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }
    
    // jdk1.8默认垃圾回收器
    // CMS
    // G1

}

题2：多线程

多线程下返回值？线程安全的吗？你理解的线程安全

import java.util.ArrayList;
import java.util.List;

public class Test {

    public static void main(String[] args) {
        method1(123);
    }

    public static List method1(int id) {
        List list1 = new ArrayList();
        list1.add(id++);
        return method2(list1);
    }

    private static List method2(List list1) {
        List list2 = new ArrayList();
        list2.addAll(list1);
        list2.remove(list1);
        return list2;
    }

}

题2.5：线程

以下代码有问题吗？为什么？

public class Test {

    public static void main(String[] args) {

        Thread thread = Thread.currentThread();
        while (true) {
            if (thread.isInterrupted()) {
                break;
            }
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

题3：锁的升级过程

题3.5：CAS原理

题4：网络IO模型

bio、nio、aio、selector、poll、epoll

题5：组件/中间件

Redis集群、Master选举算法、MongoDB、ES算法、RocketMQ/Kafka等