serialization in java interview questions

COSCO Java interview question zzz COSCO Java interview questions Java training materialsI. Java language1. Three basic features of object-oriented2. Concepts and differences between method overloading and method Rewriting3. Features of interfaces, internal classes, and abstr

after the real object is called.Proxy mode,The proxy class and the proxy class implement the same interfaceAn instance of a proxy class in a proxy classBehavioral patterns: Focus on communication between objectsSuch as: Responsibility chain mode, iterator mode, command modeResponsibility chain ModelSimilar interceptors, etc.Command mode:Separates callers from Callee's behaviorInterpreter mode:Each syntax is an interpreter classIterator mode:Change the collection class's view traversal and add a

incompatible, or if you want it to be incompatible, increment the version number manually.1->2->3 .....The second approach is to generate a hash value based on the structure of the class. Adding or subtracting a property, method, etc. can cause this value to change. I think this is the way to apply this scenario:Developers think that each time the class is modified to generate a new version number, do not want backward compatibility, the operation is to delete the original SERIALVESIONUID decla

the occurrence of Phantom read.Both Phantom and non-repeatable reads read another transaction that has already been committed (this is different from the dirty Read), and the difference is that the non-repeatable read query is the same data item, and the Phantom Read is for a whole group of data (such as the number of data).Now look at the four isolation levels that the MySQL database provides to us:①serializable (serialization): Can avoid dirty read

statement.(2) The use of reflective means. Call the Newinstance () method of the Java.lang.class or Java.lang.reflect.Constructor class.(3) Call the object's clone () method. A photocopy of an existing object in memory.(4) The use of anti-serialization means. Restores the object of the class from the file.7.ArrayList list = new ArrayList (20); How many times in the list is expanded?A 0 B 1 C 2 D 3Answer: AResolution: The default ArrayList length is 1

similarities and differences between synchronized and Java.util.concurrent.locks.Lock? Main similarities: Lock can complete all functions implemented by synchronizedMain differences: Lock has more precise line semantics and better performance than synchronized. The synchronized automatically releases the lock, and lock must require the programmer to release it manually, and must be released in the finally clause.21. What happens when I use synchronization on a static method? When a static metho

the object passivation time through the configuration file---object How long it takes to not be passivatedUnder Meta-inf, create a context.xml that reads as follows:@Overridepublic void sessionwillpassivate (Httpsessionevent se) {System.out.println ("Being passivated ... ");}@Overridepublic void sessiondidactivate (Httpsessionevent se) {SYSTEM.OUT.PRINTLN ("Being activated ... ")；}When the specified servlet project is accessed, the "passivation" appears after the set time, and then any file und

: hibernate always uses the locking mechanism of the database, never locking objects in memory! Just specify the isolation level for the JDBC connection, and then let the database take care of everything.class Lockmode defines the different locking levels required for hibernateLockmode.upgrade,lockmode.upgrade_nowait,lockmode.read;hibernate refused connection, server crashes cause1. DB does not open 2. There may be a problem with the network connection 3. The connection configuration is 4 wrong.

rewrite the aof file, the performance impact of this persistence is minimal, but the aof file will continue to grow, aof file over the General Assembly to affect the recovery speed of master restart. Master should not do any persistent work, including memory snapshots and aof log files, in particular, do not enable memory snapshots to persist, if the data is more critical, a slave open aof backup data, the policy is synchronized once per second. Master calls bgrewriteaof rewrite aof file, a