There is a detailed introduction to the operation of jar packages in java

Why use jar package and what is jar package

After the .java file is compiled, a .class file is generated. If it is written directly in other programs Or it would be inconvenient to provide it to others, so package some .class files into a jar package. The jar package can also contain some resource files (such as txt files, html files, css files, etc.), and a manifest file META -INF/MANIFEST.MF.

.class file is platform independent, so the jar package is cross-platform. If it is an executable jar package, the manifest file will contain the Main-Class attribute, indicating the Main method entry.

How to build a jar package

There are two classes as follows, Welcome class and Teacher class

package com.imooc.jardemo1;
import com.imooc.jardemo1.impl.Teacher;;

public class Welcome {
	public int num;
	public static void main(String[] args) {
		Teacher.greeting();
		Welcome welcome=new Welcome();
		Teacher lee=new Teacher();
		welcome.addTeacher(lee, 1, "gil");
		welcome.getTeaInfor(lee);
	}
	public void addTeacher(Teacher teacher,int id,String name) {
		teacher.id=id;
		teacher.name=name;
	}
	public void getTeaInfor(Teacher teacher) {
		String str="ID:"+teacher.id+" Name:"+teacher.name;
		System.out.println(str);
	}
}

rrree

Recommended online video tutorial: java learning Video

Right-click the project-Export

Select Runnable Jar file

The picture below The first box selects the entry file, the second box is the location and name of the exported Jar package, click Finish

to complete the packaging.

How to use the jar package

Create a new folder lib in the project directory: New->Folder, file name lib, you will need to use Copy the jar package into it

#Add the jar package to the build path: Right-click on the jar package that needs to be used->Build path->Add to build Path

Writing the test class JarTest, you can use the classes, methods, etc. in the Jar package (will be automatically imported)

package com.imooc.jardemo1.impl;

public class Teacher {
	public String name;
	public int id;
	public static void greeting() {
		System.out.println("Welcome!");
	}	
}

Summary:

The advantage of using jar packages is to package a bunch of files into one file for easy use.

This article is recommended to everyone by the java introduction column. You can come to this column to communicate and learn together.

The above is the detailed content of There is a detailed introduction to the operation of jar packages in java. For more information, please follow other related articles on the PHP Chinese website!