luk Hann

Ranch Hand

Posts: 48

posted 16 years ago

Hi,

To calculate standard deviation, I wrote the following program:

import java.lang.Math.*;

public class StandTest {

public static void main(String args[]) {

Stat record = new Stat();

record.addValue(2);

try {

System.out.println("Standard Deviation is" + Math.sqrt());

} catch (Exception e) {

System.out.println("Exception" + e.getMessage());

}

}

}

import java.lang.Math.*;

public class Stand {

private int N;

private double S;

private double S1;

private double SoS;

public void addValue(double d) {S +=d; S1 = (d*d); SoS+=S1; N++;}

public static double Math.sqrt() throws Exception {

if (N < 0) {

throw new Exception("negative value is not allowed");

}

return ((N*SoS)-(S*S))/(N*(N-1));}

}

When I complied it, two error messages:

Stand.java:9: ';' expected

public static double Math.sqrt() throws Exception {

^

StandTest.java:12: sqrt(double) in java.lang.Math cannot be applied to () System.out.println("Standard Deviation is" + Math.sqrt());

Why? Thanks.

luk

To calculate standard deviation, I wrote the following program:

import java.lang.Math.*;

public class StandTest {

public static void main(String args[]) {

Stat record = new Stat();

record.addValue(2);

try {

System.out.println("Standard Deviation is" + Math.sqrt());

} catch (Exception e) {

System.out.println("Exception" + e.getMessage());

}

}

}

import java.lang.Math.*;

public class Stand {

private int N;

private double S;

private double S1;

private double SoS;

public void addValue(double d) {S +=d; S1 = (d*d); SoS+=S1; N++;}

public static double Math.sqrt() throws Exception {

if (N < 0) {

throw new Exception("negative value is not allowed");

}

return ((N*SoS)-(S*S))/(N*(N-1));}

}

When I complied it, two error messages:

Stand.java:9: ';' expected

public static double Math.sqrt() throws Exception {

^

StandTest.java:12: sqrt(double) in java.lang.Math cannot be applied to () System.out.println("Standard Deviation is" + Math.sqrt());

Why? Thanks.

luk

Val Dra

Ranch Hand

Posts: 439

posted 16 years ago

If i am wrong someone will correct me on this , But if class is final it's methods are final implicitly. Math class is final therefore you can't overwrite it's sqrt Method plus if i am wrong on this too sqrt takes a parameter which value to take square of. Let me feel the heat

Val SCJP <BR>going for SCJD