sorting using comparable

[redmaverick]

I am unable to execute these codes. This code is a replica from a website.

I used Testing.java and Person.java. Should the files be named comparable.ex01.Testing.java and comparable.ex01.Person.java?

As I am pretty new to java I have this doubt.

package comparable.ex01;

import java.util.Arrays;
import java.util.ArrayList;

public class Testing {

  public static void main(String[] args) {
    Person[] persons = new Person[4];
    persons[0] = new Person();
    persons[0].setFirstName("Elvis");
    persons[0].setLastName("Goodyear");
    persons[0].setAge(56);

    persons[1] = new Person();
    persons[1].setFirstName("Stanley");
    persons[1].setLastName("Clark");
    persons[1].setAge(8);

    persons[2] = new Person();
    persons[2].setFirstName("Jane");
    persons[2].setLastName("Graff");
    persons[2].setAge(16);

    persons[3] = new Person();
    persons[3].setFirstName("Nancy");
    persons[3].setLastName("Goodyear");
    persons[3].setAge(69);

    System.out.println("Natural Order");

    for (int i=0; i<4; i++) {
      Person person = persons[i];
      String lastName = person.getLastName();
      String firstName = person.getFirstName();
      int age = person.getAge();
      System.out.println(lastName + ", " + firstName + ". Age:" + age);
    }

    Arrays.sort(persons);

    System.out.println();
    System.out.println("Sorted by age");

    for (int i=0; i<4; i++) {
      Person person = persons[i];
      String lastName = person.getLastName();
      String firstName = person.getFirstName();
      int age = person.getAge();
      System.out.println(lastName + ", " + firstName + ". Age:" + age);
    }
  }
}

package comparable.ex01;

class Person implements Comparable {
  private String firstName;
  private String lastName;
  private int age;

  public String getFirstName() {
    return firstName;
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public void setLastName(String lastName) {
    this.lastName = lastName;
  }

  public int getAge() {
    return age;
  }

  public void setAge(int age) {
    this.age = age;
  }

  public int compareTo(Object anotherPerson) throws ClassCastException {
    if (!(anotherPerson instanceof Person))
      throw new ClassCastException("A Person object expected.");
    int anotherPersonAge = ((Person) anotherPerson).getAge();  
    return this.age - anotherPersonAge;    
  }
}

[kolan]

I tried executing your code. Works for me.

I think that you are not putting the files in the right package folders.

Try executing them by putting them under comparable/ex01/Testing.java and comparable/ex01/Person.java

should work.

Other thing.. as you said you are new to java I hope that you have set the classpath correctly.

[redmaverick]

hi.... I created package/ex01/Person.java and it compiled.
however when I try package/ex01/Testing.java it is not compiling

C:\Users\comparable\ex01>javac Te
Testing.java:9: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
Person[] persons = new Person[4];
^
Testing.java:9: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
Person[] persons = new Person[4];
^
Testing.java:10: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
persons[0] = new Person();
^
Testing.java:15: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
persons[1] = new Person();
^
Testing.java:20: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
persons[2] = new Person();
^
Testing.java:25: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
persons[3] = new Person();
^
Testing.java:33: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
Person person = persons[i];
^
Testing.java:46: cannot find symbol
symbol : class Person
location: class comparable.ex01.Testing
Person person = persons[i];
^
8 errors

please let me know where I am going wrong

[kolan]

It works fine on my machine. Here is what I get as output:

E:\java-work\comparable\ex01>javac Person.java

E:\java-work\comparable\ex01>javac Testing.java

E:\java-work\comparable\ex01>java Testing
Natural Order
Goodyear, Elvis. Age:56
Clark, Stanley. Age:8
Graff, Jane. Age:16
Goodyear, Nancy. Age:69

Sorted by age
Clark, Stanley. Age:8
Graff, Jane. Age:16
Goodyear, Elvis. Age:56
Goodyear, Nancy. Age:69

E:\java-work\comparable\ex01>

I had the same problem previously. Everything worked fine after setting the classpath correctly.

Here are some links which might help you.

http://forums.sun.com/thread.jspa?threadID=670019

http://forums.sun.com/thread.jspa?threadID=753450

http://www.sharkyforums.com/showthread.php?t=281641

Try including the current directory in your classpath.

[redmaverick]

Thanks for the help! The first thread showed me how to fix the problem. I used
javac -cp . comparable/ex01/Testing.java to compile
I dint change the path because it worked fine for many other java programs.

[dlorde]

You need your classpath set correctly. You may find this tutorial helpful: Path & Classpath.

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