How to call a method function from another class

Question

I m writing a java project that has three different classes  This is what i have have so far  I m just stuck on how do you call a method function from another class to another class  I have written 2 classes already  I got the  Date  class and  TemperatureRange  class done  now i m trying to call those 2 classes into  WeatherRecord  class  I m not sure if i m explaining this right    public class WeatherRecord   implements Record        private String TemperatureRangetoday      private String TemperatureRangenormal      private String TemperatureRangerecord        public static void main  String   args              This is another class  public class Date       public static String date String date  String month  String year           String rdate   date        month        year          return rdate               And here s another class  public class TemperatureRange       public static String TempRange  String high  String low            String rTempRange   high   high        low  low           return rTempRange

User · Answer

You need to understand the difference between classes and objects. From the Java tutorial:

An object is a software bundle of related state and behavior

A class is a blueprint or prototype from which objects are created

You've defined the prototypes but done nothing with them. To use an object, you need to create it. In Java, we use the new keyword.

new Date();

You will need to assign the object to a variable of the same type as the class the object was created from.

Date d = new Date();

Once you have a reference to the object you can interact with it

d.date("01", "12", "14");

The exception to this is static methods that belong to the class and are referenced through it

public class MyDate{
  public static date(){ ... }
}

...
MyDate.date();

In case you aren't aware, Java already has a class for representing dates, you probably don't want to create your own.

User · Answer

You need to instantiate the other classes inside the main class   Date d   new Date params   TemperatureRange t   new TemperatureRange params     You can then call their methods with   object methodname params   d method      You currently have constructors in your other classes  You should not return anything in these   public Date params       set variables for date object     Next you need a method to reference   public returnType methodName params     return something

User · Answer

For calling the method of one class within the second class  you have to first create the object of that class which method you want to call than with the object reference you can call the method  class A      public void fun           do something         class B      public static void main String args          A obj   new A         obj fun            But in your case you have the static method in Date and TemperatureRange class  You can call your static method by using the class name directly like below code or by creating the object of that class like above code but static method  mostly we use for creating the utility classes  so best way to call the method by using class name  Like in your case - public static void main  String   args     String dateVal   Date date  quot 01 quot   quot 11  quot 12 quot       calling the date function by passing some parameter     String tempRangeVal   TemperatureRange TempRange  quot 80 quot   quot 20 quot

User · Answer

You need a reference to the class that contains the method you want to call  Let s say we have two classes  A and B  B has a method you want to call from A  Class A would look like this   public class A       B b     A reference to B      b   new B       Creating object of class B      b doSomething        Calling a method contained in class B from class A     B  which contains the doSomething   method would look like this   public class B       public void doSomething                 System out println  Look  I m doing something in class B

User · Answer

In class WeatherRecord   First import the class if they are in different package else this statement is not requires  Import  lt path gt  ClassName    Then  just referene or call your object like   Date d  TempratureRange tr  d   new Date    tr   new TempratureRange    this can be done in Single Line also like      Date d   new Date        But in your code you are not required to create an object to call function of Date and TempratureRange  As both of the Classes contain Static Function   you cannot call the thoes function by creating object     Date date date month year        this is enough to call those static function     Have clear concept on Object and Static functions  Click me

[java] How to call a method function from another class?

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