java - Run the methods of a class from another class -

i have 4 classes in java package. 1 class has main() method.

how can run methods in 4 classes when class when run main() method?

here classes:

cat1.java

package test;  public class cat1 {      public cat1() {         system.out.println("100");     }      public cat1(int ){         = 10;         system.out.println(" cat1 :"+ i);     } } 

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cat2.java

package test;  public class cat2 extends cat1 {      public cat2() {         system.out.println("200");     }      public cat2(int ){         super();         system.out.println("cat 2 ; "+ i);     } } 

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cat3.java

package test;  public class cat3 extends cat2{      public cat3() {         system.out.println("300");     }      public cat3(int i){         super();         system.out.println("cat 3 : "+ i);     }  } 

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sample.java

package test;  import java.text.dateformat; import java.util.calendar; import java.util.locale;  public class sample {      /**      * @param args      */     public static void main(string[] args) {          calendar cal = calendar.getinstance();          //date d = cal.gettime();         locale locale = new locale("en");         dateformat dateformat = dateformat.getdateinstance(dateformat.full, locale);         system.out.println(" long date : " + dateformat.format(cal.gettime()));          string incomedata = "200,2,2,2,2";           int expense = 0;         string expensesplit = incomedata;         system.out.println(" e");         string expensearray[] = expensesplit.split(",");         string income = expensearray[0];         (int = 1; < expensearray.length; i++) {             expense = expense+integer.parseint(expensearray[i]);         }         system.out.println(" income "+ income);         system.out.println(" expense "+ expense);       }  } 

looks new object , invoke function need.
such

cat3 cat3 = new cat3(); 

or want call automatically when main() method run?