Problem to call the event

Do you have that JLib2.jar in the classpath for the JLib3 project? Otherwise the compiler won't know anything about it.

Yes, I did add this jar to JLib3 project.

If the .jar file is in the .zip file, get the .zip file on your machine and unzip it.
Then add the .jar file to your classpath.
If you run from the command line, something like:

java -cp ./JLib2.jar  CalC13

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Sorry, I did add the jar file to JLib3. Can you please advise what is wrong inside it attached below?
https://dl.dropboxusercontent.com/u/40211031/JLib3.zip

I am using Eclipse.

In Eclipse, did you add it to your project?

If not, right-click the project and select Build Path / Add External Archives..., then select your .jar file.

I already attach jar file to the project (see the attached)
t966.png

In your import statement, do not use the jar file name.
Instead use the package name for the class followed by the class name.
For example, if you want to use the TimeUnit class from the standard java library, the import statement is:
import java.util.concurrent.TimeUnit

The package name, java.util.concurrent, is followed by the class name, TimeUnit

Thanks. I try to use package name instead

package CalCl3;
import CalCl.CalCl;

public class CalCl3 implements CalCl {

}

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but I still get this

Description	Resource	Path	Location	Type
The type CalCl cannot be a superinterface of CalCl3; a superinterface must be an interface	CalCl3.java	/JLib3/src/CalCl3	line 4	Java Problem

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Many many thanks. One last thing, to these codes

package CalCl3;
import CalCl.CalCl;

public class CalCl3 extends CalCl {
	System.out.println(Float.toString(computePayment(4000,0.5,3000,4)));
}

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how to correct these problems?

Description	Resource	Path	Location	Type
Return type for the method is missing	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error on token "println", invalid AnnotationName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error on tokens, delete these tokens	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ";" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ";" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MemberValue	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "}" to complete ClassBody	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "Identifier (" to complete MethodHeaderName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "Identifier (" to complete MethodHeaderName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "SimpleName" to complete QualifiedName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem

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Ni hao ma wo de pengyou.

Line 5 should be inside a method which must have a return type (void if you don't return anything).
If you don't already have a main method, add one like this inside your CalCl3 class:

    public static void main(String[] args) {
        System.out.println(Float.toString(computePayment(4000,0.5,3000,4)));
    }

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Mark,
You're very nice! And do you expect to talk in Mandarin?

I still get these

Description	Resource	Path	Location	Type
Return type for the method is missing	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error on token "println", invalid AnnotationName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error on tokens, delete these tokens	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ";" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ";" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MemberValue	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert ")" to complete MethodDeclaration	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "}" to complete ClassBody	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "Identifier (" to complete MethodHeaderName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "Identifier (" to complete MethodHeaderName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem
Syntax error, insert "SimpleName" to complete QualifiedName	CalCl3.java	/JLib3/src/CalCl3	line 5	Java Problem

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to these codes.

package CalCl3;
import CalCl.CalCl;

public class CalCl3 extends CalCl {
	public static void main(String[] args) {
        System.out.println(Float.toString(computePayment(4000,0.5,3000,4)));
    }
}

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Many thanks Mark.
I now only get this

Description	Resource	Path	Location	Type
Cannot make a static reference to the non-static method computePayment(double, double, double, int) from the type CalCl	CalCl3.java	/JLib3/src/CalCl3	line 6	Java Problem

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to these codes.

package CalCl3;
import CalCl.CalCl;

public class CalCl3 extends CalCl {
	public static void main(String[] args) {
        System.out.println(Double.toString(computePayment(4000,0.5,3000,4)));
    }
}

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Here is JLib2 project
https://dl.dropboxusercontent.com/u/40211031/JLib2.zip

inside which jar file also included.

Many thanks Mark.
I get these problem

Description	Resource	Path	Location	Type
Illegal modifier for the class CalCl; only public, abstract & final are permitted	CalCl.java	/JLib2/src/CalCl	line 3	Java Problem
Syntax error, insert ";" to complete LocalVariableDeclarationStatement	CalCl3.java	/JLib3/src/CalCl3	line 7	Java Problem

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to declare it as static

package CalCl;

public static class CalCl {
    
	public double computePayment(
            double loanAmt,
            double rate,
            double futureValue,
            int numPeriods) {
		double interest = rate / 100.0;
		double partial1 = Math.pow((1 + interest), 
		              - numPeriods);
		double denominator = (1 - partial1) / interest;
		double answer = (-loanAmt / denominator)
		              - ((futureValue * partial1) / denominator);
		return answer;
	}
}

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If the class is static, the method must be static also. Add the static keyword to the computePayment class.

The other option is #2 from my previous comment.

Sorry, I still get this

Description	Resource	Path	Location	Type
Illegal modifier for the class CalCl; only public, abstract & final are permitted	CalCl.java	/JLib2/src/CalCl	line 3	Java Problem

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to these

package CalCl;

public static class CalCl {
    
	public static double computePayment(
            double loanAmt,
            double rate,
            double futureValue,
            int numPeriods) {
		double interest = rate / 100.0;
		double partial1 = Math.pow((1 + interest), 
		              - numPeriods);
		double denominator = (1 - partial1) / interest;
		double answer = (-loanAmt / denominator)
		              - ((futureValue * partial1) / denominator);
		return answer;
	}
}

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Use option 2.

How to correct the problem now, to JLib2, that is giving the jar file?