what is elasticsearch in java

another protocol. It does not refer to com interfaces, CORBA interfaces, Java interfaces, Delphi interfaces, man-machine interfaces, or Nic interfaces. In specific implementation, the UML interface can be implemented as a language interface, an interface in a distributed object environment, or any other interface, but in terms of understanding the UML interface, the implementation of each part of the system works together through the Protocol defined

What is the difference between an abstract class and an interface?1, abstract class in the Java language is represented by an inheritance relationship, a subclass can only inherit a parent class. However, multiple interfaces can be implemented.2, in the abstract class can have their own member variables and non-abstrac

type modifier (typespecifier). It is designed to modify variables that are visited and changed by different threads. Variables defined by the volatile type are extracted directly from the corresponding memory each time the system uses it, rather than using the cache. After using the volatile modifier member variable, the values of the variables that all threads see at any time are the same. A demo sample using volatile

synchronization method than a mutex The acquisition of the lock in the critical section is called entering the critical zone; And the release of the lock is called leaving the critical section. Differences (with semaphores and mutexes) Mutexes and semaphores are visible in any process of the system; In other words, a process creates a mutex or semaphore, and another process attempts to acquire the lock

difference between = = and JavaScala's = = follows the comparison rules:First check whether the left side is null, if not, call the left manipulation data of the Equals method. Therefore, the exact comparison depends on the definition of the Equals method that makes the operation. Because of the automatic null check, there is no need to manually check it again.java = = can compare primitive types or refere

be type-detected, or the array itself is holding the object, and the generic container is only in the compiler to check type safety, and in the run time is all object, only half-definition, or the generic container does not hold objects, it will lead to the above problems.Summary: In this chapter we mainly compare arrays with generic containers and observe

Click to enter _ more _java FAQ-base Class Library1, Java.math package has what functionThe Java.math package provides a mathematical class in Java. Includes basic floating-point libraries, complex operations, and arbitrary-precision data operations. Main classes such as:?The classes in math are described below: arbitrary length shapingBigInteger, the arbitrary length of the non-variable shaping. Beca

Click to enter _ more _java thousand ask1, meta-annotation is whatSee the comments here: what is the commentUnderstanding custom Annotations See here: How to customize annotationsMeta annotations are responsible for annotating other annotations. Java 5 defines 4 standard meta-annotations (meta-annotation): @Target, @Re

encoding is the process of turning a string into a byte, and decoding is the process of turning a byte into a string according to the corresponding encoding . a Good article: Understanding coding from the principle-what exactly is coding? What

Click to enter _ more _java thousand ask1. What is ATTACHAPI?The Attach API is a set of extension APIs provided by Sun, which is not a standard Java API. As the name implies, Attach, some programs are attached to the JVM. Simply put, a program

"Interface is a specification," that's right."It would be easier to write the implementation method directly in this class," How do you ensure that the interface is implemented in a class? If more than one class implements the same interface, how does the program know that they are related?Since it is not a class to achieve, it

Nested class does not depend on an instance object of an external class,static Nested class can access the non- static The member variable . 5. When you access staticnestedclass, You can direct use static Nestedclass , without the need to add the name of the outer class, in staticnestedclass static member variable , you do not need to add the name of the external class. The inner class defined in the static method is also static Nestedclass

For wait and sleep it would seem to block threads, but they are really a big difference, so here's a little bit of discussion: Difference one, Sleep () is the method inside the thread, and wait () is the method of the object class.This is relatively simple, directly read the code will know: The difference between the sleep () method does not need to be a

Heroes, the Java Thread.CurrentThread () what role ah. 397458726 | Browse 10,631 times 2009-09-16 13:39 2009-09-16 13:52 Best Answer Thread.CurrentThread () can get a reference to the current thread, typically by Thread.CurrentThread () when there is no thread object and need to obtain thread information.This answer is

What is generic?First, we will write a simple generic class to illustrate:[Java]Public class Generics Private T o; // generic member variablePublic Generics (T o ){This. o = o;}Public T getObject (){Return o;}Public void setObject (T o ){This. o = o;}Public String getType (){Return o. getClass (). getName ();}}This generic class includes its own constructor, And

very prone to java.lang.ClassCastException anomalies(This example, I found in a blog, I can read the introduction of the generic example, but I executed the error, the wrong content is java:4: Error:cannot Find Symbol, may be my JDK version is wrong, I want to put the example of generics as soon as possible to finish, This mistake will be put here for the time b