You need to extends this class to your class. And then override the method you want to change.

Example :

public YourClass extends ParameterTool {

@Override

//Here goes the method your want...

}

See the page 'Java: Packages and Import' (https://www.leepoint.net/language/10basics/import.html)

The statement "package" is used to indicate that the class being implemented is part of a group of related classes placed in the same folder, in your example:

package org.apache.flink.streaming.examples.windowing;

is indicated that the class is in a folder named "windowing", and this folder is inside the folder "examples", and so on.

On the other hand, the statement "import" is used to indicate that the class being implemented uses a class or a group of classes from some "package". This instruction helps to locate the libraries used in your class.

In your example:

import org.apache.flink.api.java.utils.ParameterTool;

is indicated that the class being implemented can use one instance of the ParameterTool class.

In simple words, Package is used to group (create) classes into a single name whereas import is used to use the instance of a class/es

Thank you all for your answers.

Let me extend my question to be more precise.

I need to change /override some functions in ParameterTool class which is imported as

import org.apache.flink.api.java.utils.ParameterTool;

How can I do this?

Thank you again.

You need to extends this class to your class. And then override the method you want to change.

Example :

public YourClass extends ParameterTool {

@Override

//Here goes the method your want...

}

Assalam-o-Alaikum Dear,

Hi Dear if you have a some Knowledge about programming libraries. for Example in C or C++ ( string.h, stdlib.h, conio.h etc). If you are using any additional or Third party function in your program you most to import or include in your program ...

But Package means in Java you collect your files or Classes file in one folder. For example in a project Network related classes are in one folder and Database related classes are in other folder and so on...

https://www.guru99.com/java-packages.html

The Frank answer is correct. I merely want to add that there are several rules to override methods in Java, such as:

- The overriding method must have same argument list.

- The overriding method must have same return type (or subtype).

Please check the next link:

http://www.codejava.net/java-core/the-java-language/12-rules-of-overriding-in-java-you-should-know

Best regards

Note also that, if you extend a class, it behaves slightly differently if you put it in the same package as its parent class or not. Indeed, variables or methods/members can be public, private or protected. The way these modifiers act is explained at https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html

Rough summary:

- public members are always accessible

- private members are never accessible from outside a class

- protected members are accessible from an extended class only if it is in the same package as the parent class.

package is public access, mean if A have access to B and B packages C, then A can also have access to C.

in import it is private access, mean if A have access to B and B imports C, then A cannot have access to C.

I don't understand the previous answer.

package is public access, mean if A have access to B and B packages C, then A can also have access to C.

Are B and C packages?

If this is true, what does it mean: B packages C?

If I use import, from where the file is imported?

- From your classpath at compile or runtime.

and if I use package where can I find the source file?

- Usually in a packagename.src.jar or similarly named file.

Infact, I found these two files in source code but when I change these files or even delete these, the program still compiles and run normally.

- Running java code only requires the compiled forms, or .class files. Check your classpath and sourcepath.

How can I trace the exact location of these imports / packages?

- If you want source and class files to be in same location, use classpath only. If you want them separated, use classpath and sourcepath with different locations. The location of imported packages comes from jars or classes on the classpath. The location of related source to imported packages is typically in another jar (source jar) or possibly in a source path. Best practice is to separate classes into jars and source in source jars, named similarly.

Thank you Bryan Mckiney for your concrete answer. It is very beneficial for me.

Package contains the class or differents class which you can include in your project or class of your project but import facilitate you to call or include some class's that contain your package in your project.

For exemple if I want to use the DATE in my class, I must IMPORT the class which contain it from the package like this:

import java.util.*; that mean you include all class contains in that package and you can use it wantever you want.

That must be used bellow in your class.

Thank you