How to call String value one class to another class in Java

I think you misunderstood the main method, maybe I am wrong, however only one main method is executed.

If you run Sample2.main - on Sample1 you are not setting a name so it is null (Sample1.main is never executed).

If you run Sample1.main - Sample1 is created and assigned a name.

So either assign the name in the Sample2.main:

public static void main(String[] args) {
  Sample1 n2= new  Sample1();
  n2.setName("xxx");
  System.out.println(n2.getName());
}

or do it via constuctor.

public class Sample1 {
  private final String name;
  public String getName() {
    return name;
  }
  public Sample1(String name) {
    this.name = name;
  }
}

Consider the code :

Sample1 n2= new  Sample1();
System.out.println(n2.getName());

Here the Name is not set , So you need to set the name before getting the name.

Sample1 n2= new  Sample1();
n2.setName("name goes here");
System.out.println(n2.getName());

Also, you can try parameterized constructor in the Sample1 class and access like in sample2 class:

Sample1 n2= new  Sample1("your name goes here");
System.out.println(n2.getName());

The constructor will be :

public Sample2(String name){
this.name = n;
}

3 thing you can add method in Sample1 class and access it in Sample2 class.

I don't want to set String value in Sample2 class, need to assign string value in Sample1 only, after that i need that string value in Sample2 class

    public class Sample1 {
    private String _name;
    public String getName() {
        return _name;
    }
    private setName(String name) {
        _name = name;
    }
    public SetNameHelper(){
       setName("somestring");//You will be setting the name in Sample 1
    }
}


public class Sample2 {
    public static void main(String[] args) {
        Sample1 n2= new  Sample1();
        n2.SetNameHelper();
        System.out.println(n2.getName());//You will be getting Name in Sample 2 class
    }
}

class Sample2 {

Sample1 sample1;

Sample2(Sample1 sample){
    this.sample1 = sample;
}

private String getSample1Name() {
    return this.sample1.getName();
}

public static void main(String[] args) {

    Sample1 sample1 = new Sample1();
    sample1.setName("Abc");

    Sample2 n2= new  Sample2(sample1);
    System.out.println(n2.getSample1Name());
}

}

I think I understand you confusion: you mistake a main function for a constructor!

I noticed that you created a main function in each class, whose only role is to create an instance and set the internal fields of the class. It's probably a Constructor you were looking for.

Here's the deal:

• A main method is the entry point of a program. It just stays, to run me: begin executing this code. You probably (99.9% of the case) need only one main method per project.
• A Constructor is a method which creates an instance of, each class, i.e. an object you can manipulate elsewhere in your code. Read up on Object-Oriented Programming

So here is your example, fixed (I believe), in a way that can bring sample1 value into an sample2, as you say:

public class Sample1 {

    public String name;
    public String Sample1(String initialName){
         this.name = initialName;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

public class Sample2{
    public String name;
    public String Sample2(String initialName){
         this.name = initialName;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

public class ProgramEntryPoint{
    public static void main(String[] args) {
        Sample1 s1 = new  Sample1("a name");
        System.out.println("Initial sample1 name: " + s1.getName());
        s1.setName("a New Name!");
        System.out.println("New sample1 name: " + s1.getName());

        Sample2 s2 = new Sample2(s1.getName());
        System.out.println("Initial sample2 name: " + s2.getName());
    }
}

Which, once you run ProgramEntryPoint.main, will print:

Initial sample1 name: a name
New sample1 name: a New Name!
Initial sample2 name: a New Name!

This is all simple Java stuff, you should read up a few basic tutorials (the ones on oracle website are a good start)