Let’s push a book first: java programming ideas, although the content is noisy and boring, please read it patiently~ (233333, it is a spur to yourself, hey)
It is recommended to understand these terms through practical operation, otherwise it will be too painful to simply watch.1. IDE
Integrated Development Environment (IDE, Integrated Development Environment) is an application used to provide a program development environment, generally including tools such as code editors, compilers, debuggers, and graphical user interfaces. Such as Microsoft's Visual Studio series, Borland's C++, Builder, Delphi series, and then IBM's eclipse series.
2. JDK
JDK (Java Development Kit) is a software development kit (SDK) for the Java language. The JDK contains JRE. There is a directory named jre in the JDK installation directory. There are two folders bin and lib. Here, it can be considered that the bin is jvm, and lib is the class library required for jvm work. , and jvm and lib together are called jre. JDK is the core of the entire JAVA, including the Java runtime environment JRE (Java Runtime Environment), a bunch of Java tools (javac/java/jdb, etc.) and Java-based class libraries (ie, Java API including rt.jar).
3. JRE
Java Runtime Environment (Java Runtime Environment), a collection of environments necessary to run JAVA programs, including JVM standard implementations and Java core class libraries. JRE is a Java runtime environment, not a development environment, so it does not contain any development tools (such as compilers and debuggers)
4. JVM
The java virtual machine is what we often call the java virtual machine. It is the core part of the cross-platform implementation of the entire java. All java programs are first compiled into .class class files, which can be executed on the virtual machine. That is to say, the class file does not directly correspond to the operating system of the machine, but indirectly interacts with the operating system through the virtual machine, and the virtual machine interprets the program to the local system for execution. The JVM shields the information related to the specific operating system platform, so that the Java program only needs to generate the object code (bytecode) running on the Java virtual machine, and it can run on various platforms without modification.
5. API
application programming interface. Interface description for a software package or "toolbox". For example, Alipay can transfer money to the bank because Alipay calls the bank-related API interface. The API contains all the classes or subroutines in the toolbox and their usage instructions.
6. Abstract classes
Simply put, it is a class decorated with abstract. It abstracts the common attributes and methods of multiple objects into a class. For example, if I define an abstract "person" class, what are the common attributes between each person? (height, gender, age, etc.), these can be included in abstract classes, abstract classes cannot create objects, and are mainly used to create subclasses. Like I create Student class, Teacher class etc through "Person" class.
Subroutine parameters are called declarations. When the call executes, the value is passed to the self function by declaration. Arguments are also called "parameters". That is, when you call a function, it is written in parentheses to assign values to formal parameters. ( See the code below)
8. Formal parameters
Also called formal parameters, corresponding to actual parameters. It is the parameter used when defining the function name and function body, and the purpose is to receive the parameters passed in when calling the function.
class Test{
int temp; // global variable
void function(int a,int b){//a,b, are formal parameters, accept actual parameters
int c=1;//local variable
}
public static void main(String args[])
{
int a=1;//a,b are actual parameters, actual parameters
int b=2;
function(a,b)//The function function is called at this time, where a and b are actual parameters
}
}
9.
Global variables
refer to those declared outside the function body, and the life cycle is the same as that of the program. It can be updated in different function bodies under the same program, which is exhausting.
10. Local variables A variable
declared in a function has the same life cycle as the function body in which it is located. It is only created when someone calls it, and usually sleeps.