Programmer Think

In some business scenarios, we need two identical but unrelated java objects. For example, using prototype mode, multi-threaded programming, etc. java provides the concept of deep copy. Through deep copy, a target object can be perfectly copied from the source object, which is the same but independent of the source object. Same here means that ...

I. Multi-table Association Query Example: SQL> create table student1 ( sid varchar(3), sname varchar(6), sage number(3)); Table created. SQL> create table course1 ( sid varchar(3), cname varchar(8), cno number(3)); Table created. student1 table SQL> select * from student1; SID SNAME SAGE --- ------ ...

introduce LinkedBlockingQueue is the next blocked queue implemented as a single-chain table in a java Concurrent package. It is thread-safe. As to whether it is bounded, see the analysis below. Source Code Analysis Main attributes // capacity private final int capacity; // Number of elements private final AtomicInteger count = new AtomicIntege ...

Processes and threads Process is the basic unit that can run independently and allocate resources in a computer system. It is composed of PCB (process control block), data segment and code segment. It is a basic unit that can run independently. The creation, scheduling and allocation of processes require large time and space overhead. Threads ...

introduce A priority queue is a collection of 0 or more elements in which each element has a weight value and each time it leaves the queue, the element with the highest or lowest priority pops up. Generally speaking, priority queues are implemented using heaps. Source Code Analysis Main attributes // Default capacity private static fina ...

Background introduction When learning sklearn er, besides the difficulty of algorithm, we have to learn matplotlib visualization. For my practical application, visualization is more important. However, the ease of use and aesthetics of matplotlib are not complimentary. One after another, plotly and seaborn have been used and finally fixed in Bo ...

0819 self-summary session and cookie 1.django sets session request.session['name'] = username request.session['age'] = 13 A session ID of key: {"name":'username','age': 12} is automatically generated and encrypted in the latter part of django. 2. Get session request.session.get('name') 3. Five session settings in Django 1. Datab ...

Solution and analysis of the problem that sem_timedwait has been blocked by modifying system time introduce When recently fixing a project problem, it was found that when the system time was modified forward, the sem_timedwait function would be blocked all the time. By searching, it is found that int sem_time dwait (sem_t*sem, const struct tim ...

1. Small and large tables join 1.Definition //Keys are relatively dispersed and tables with small amounts of data are placed on the left side of the join, which effectively reduces the chance of memory overflow errors. //Further, you can use map ...

Delete elements Like adding elements, deleting elements first finds the bucket in which the elements are located, then uses the idea of sectional locking to lock the whole bucket, and then carries on the operation. public V remove(Object key) { // Call the Replacement Node Method return replaceNode(key, null, null); } final V replaceN ...