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Detailed example of protected keyword in java

The protected keyword means protected, visible to classes and all subclasses in the same package, and the objects used are variables and methods. The protected keyword cannot modify classes (external classes).

Jun 02, 2020 pm 04:52 PM

java protected Keywords

What are the three ways to initialize an array in java?

Java introductory program: This article introduces three ways to initialize arrays in Java. It has certain reference value and I hope it can help you. The three ways to initialize an array in Java are: 1. Static initialization; 2. Dynamic initialization; 3. Default initialization.

Jun 01, 2020 pm 03:34 PM

java initialization array

Can Java HashMap key be repeated?

Keys in Java's HashMap cannot be repeated. If added repeatedly, HashMap will automatically overwrite the data with the same key, ensuring that one key corresponds to one value. When using it, just add the data in one HashMap to another HashMap in sequence according to the key. That’s it.

Jun 01, 2020 am 10:46 AM

hashmap java

What is a configuration file in Java

Configuration file names in Java generally end with ".properties" and ".xml". The structure of these configuration files is the same as Java's HashMap structure. Its function is to modify the parameters in the code by modifying the configuration file. changes, thereby enabling flexible parameter changes.

Jun 01, 2020 am 10:29 AM

java

What are the functions of break and continue keywords in java

The break keyword is mainly used in loop statements or switch statements to jump out of the entire statement block; the continue keyword is used to make the program jump to the next iteration of the loop immediately, and is suitable for various loop control structures.

May 31, 2020 pm 03:56 PM

break continue java

Implement java threads by inheriting the Thread class

Java introductory program: This article introduces you to the method of implementing Java threads by inheriting the Thread class. It has certain reference value and I hope it can help you. The Thread class is the parent class of all thread classes and implements the extraction and encapsulation of threads.

May 30, 2020 pm 04:28 PM

java thread thread

Difference between Java constructors and normal methods

The difference between Java constructors and ordinary methods: 1. The name of the constructor must be exactly the same as the class name and there is no return type; 2. There must be a constructor in the class; 3. The constructor cannot be static, final, synchronized, abstract and native modification.

May 30, 2020 am 11:29 AM

java

How to check java version

How to check the Java version: First open the [Start] menu in the lower left corner of the computer, find the [Run] option, and click to open; then enter the "cmd" command in the pop-up run dialog box; finally enter the command "Java -version" and click Return You can check the java version by clicking on the car.

May 30, 2020 am 11:28 AM

java

What file is .jar?

In the software field, a JAR file is a software package file format, built in ZIP format, with ".jar" as the file extension. It is usually used to aggregate a large number of Java class files, related metadata and resource files into one file. In order to develop Java platform application software or libraries.

May 29, 2020 pm 04:44 PM

jar java

What to do if the java plug-in cannot be loaded

The solution to the problem that the java plug-in cannot be loaded: first open the control panel, click "Windows Firewall->Allowed Programs"; then open java, switch to the "Security" tab, and lower the security level to the lowest; then click "Change User Account" Control Settings"; finally pull down the mobile icon to "Don't notify".

May 29, 2020 am 11:55 AM

The difference between java constants and variables

The difference between Java constants and variables: 1. Constants are modified with final, but different variable types have different allocated memory types; 2. Constants must be assigned an initial value when they are declared, while variables have no default values ??for initialized members; 3. Two When performing arithmetic operations on variables with different data types, data type conversion needs to be performed first.

May 29, 2020 am 11:51 AM

java

Encapsulation, inheritance, understanding of polymorphism

Understanding of encapsulation, inheritance, and polymorphism: 1. Encapsulation is to hide the properties and implementation details of an object and provide public access to the outside world to prevent random access and modification of data; 2. Inheritance is to extend an existing class and Inherit the attributes and behaviors of the class to create a new class; 3. Multiple different implementations of the interface are polymorphism.

May 28, 2020 pm 05:47 PM

java

Java counts the number of occurrences of each character in a string

The method for Java to calculate the number of occurrences of each character in a string is: 1. Use Scanner to obtain the string entered by the user; 2. Create a Map collection; 3. Traverse the string and obtain each character; 4. In the Map collection Determine whether the key exists; 5. Traverse the Map collection.

May 28, 2020 pm 05:29 PM

java character string

What are the java modifiers?

This article comes from the Java development introductory column. It introduces the relevant knowledge of Java modifiers to everyone. It has certain reference value and I hope it can help everyone. Java modifiers are divided into: 1. Access control modifiers; 2. Non-access modifiers.

May 27, 2020 pm 05:37 PM

java modifier