从另一个类运行类的方法

Question

我的Java包中有四个类。只有一个类有main()方法。

当我运行main()方法时，如何运行四个类中的所有方法？

这里是我的课：

Cat1.java

package test; 

public class Cat1 { 

    public Cat1() { 
     System.out.println("100"); 
    } 

    public Cat1(int i){ 
     i = 10; 
     System.out.println(" cat1 i :"+ i); 
    } 
} 

---

Cat2.java

package test; 

public class Cat2 extends Cat1 { 

    public Cat2() { 
     System.out.println("200"); 
    } 

    public Cat2(int i){ 
     super(); 
     System.out.println("Cat 2 ; "+ i); 
    } 
} 

---

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); 
    } 

} 

---

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]; 
     for (int i = 1; i < expenseArray.length; i++) { 
      expense = expense+Integer.parseInt(expenseArray[i]); 
     } 
     System.out.println(" Income "+ income); 
     System.out.println(" expense "+ expense); 


    } 

} 

Answer 1

看起来像你刚才说的新对象，并调用你所需要的功能。
如

Cat3 cat3 = new Cat3(); 

或者你想自动调用，当main（）方法运行？

Answer 2

java是一种面向对象的语言，所以如果你不引用对象，它们只会坐在那里，什么也不做。在主要方法中，您可以将其视为创建对象的起点，并使用它们访问方法。

里面你main（）方法，你可以创建一些物体..

Cat1 sampleCat1 = new Cat1(); 
Cat1 anotherSampleCat1 = new Cat1(4); 

Answer 3

package test; 
import java.text.DateFormat; 
import java.util.Calendar; 
import java.util.Locale; 

public class Sample { 

    public static void main(String[] args) { 
     Cat1 cat1 = new Cat1(1); 
     Cat2 cat2 = new Cat2(2); 
     Cat3 cat3 = new Cat3(3); 
     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]; 
     for (int i = 1; i < expenseArray.length; i++) { 
      expense = expense+Integer.parseInt(expenseArray[i]); 
     } 
     System.out.println(" Income "+ income); 
     System.out.println(" expense "+ expense); 

    } 
}