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API overview API concept API(Application Programming Interface): application programming interface Also known as: help documents To write a robot program to control the robot to play football, the program needs to send all kinds of commands to the robot, such as running forward, running backward, sh ...

1. Enumeration public class TestSeason { public static void main(String[] args) { Season spring = Season.SPRING; System.out.println(spring); spring.show(); System.out.println(spring.getSeasonName()); } } //Enum Class class Season{ //1. Provide the properties of the class and declare it private final private final ...

The core point of the underlying implementation of ArrayList 1. The collection bottom layer is implemented by using array 2. Why can a set store infinite size? ####The implementation of array expansion technology Arrays.copyOf: To copy the array, return the copied array. Parameters are the copied arr ...

1, Loading mechanism of class The loader loading of classes in Java comes from files, networks, source files, etc. By default, the class loader of the jvm uses the parent delegation mechanism, Bootstrap ClassLoader, Extension ClassLoader, and attachment classloader (system classloader). Each class l ...

After JDK 1.5, enum types can be defined with the help of enum keyword. The syntax structure is as follows: [public] enum enumeration name [implements interface list]{ Enumerating object 1 [, enumerating object 2] [etc ]; [member variable 1;] [member variable 2;] [...] [(static or non static) code block] [constructi ...

Interview question 6: reconstruction of binary tree Title Description: Enter the results of the preorder traversal and inorder traversal of a binary tree, and rebuild the binary tree. It is assumed that the results of the input preorder traversal and preorder traversal do not contain duplicate numbers. For example, input the sequence {1,2,4,7,3 ...

Reflection pattern optimization of factory class with a large number of switch branches Continue with the case of factory pattern. In the previous article, there were only two algorithm classes (addition and subtraction). Now add another multiplication Step one: //Arithmetic class public class Operation { private double _numberA=0; ...

Before JDK 1.5, there was no enum keyword. If you want to use enumeration classes, programmers need to design them according to the rules of Java language. Starting from JDK 1.5, the Java language has added enum keyword, through which enumeration classes can be easily defined. This enumeration class has its own programming rules, and has some s ...

The default jdk of Maven is version 1.5. It is too cumbersome to modify the jdk version again every time you create a new project, so the following methods can modify the default jdk version of Maven. Note: it's better to update Maven's version. The setting.xml jdk13 configuration is invalid when I use ...

Yesterday we looked briefly at the use of Unsafe. Today we look at how atoms in JUC use Unsafe and how they work!   1. Simple use of AtomicLong Also remember that in the last blog we used the volatile keyword to modify a variable of type int, and then two threads did 10,000 + 1 operations on the variable, and the result wasn't 20,000. Now when ...