New to Java

Hi, everyone! I have two questions. One is about making judgment about whether a method has been called or not; another one is about how to return "String value+newline character+String value" with a return statement.
Here are the two original problems that I tried to solve.
Write a class definition of a class named 'Value' with the following:

a boolean instance variable named 'modified', initialized to false

an integer instance variable named 'val'

a constructor accepting a single paramter whose value is assigned to the instance variable 'val'

a method 'getVal' that returns the current value of the instance variable 'val'

a method 'setVal' that accepts a single parameter, assigns its value to 'val', and sets the 'modified' instance variable to true, and

a boolean method, 'wasModified' that returns true if setVal was ever called.
And I wrote my code this way:

public class Value
{
 boolean modified=false;
 int val;
 public Value(int x)
 {val=x;}
  public int getVal()
  {return val;}
   public void setVal(int y)
   {
    val = y;
    modified = true;
    }
     public boolean wasModified()
     {
      if(val==y&&modified==true)
      return true;
      }
}

I tried to let the "wasModified" method know that the "setVal" has been called by writing:
if(val==y&&modified==true)
or
if(x.setVal(y))
I supposed that only when the "setVal" is called, the "modified" variable will be true(it's false by default) and val=y, don't either of this two conditions can prove that the method "setVal" has been called?
I also have some questions about the feedback I got
class Value is public, should be declared in a file named Value.java
public class Value
cannot find symbol
symbol : variable y
location: class Value
if(val==y&&modified==true)
*^*
*2 errors*
I gave the class a name Value, doesn't that mean the class has been declared in a file named Value.java*?
I have declared the variable y, why the compiler cann't find it? is it because y has been out of scale?



The other problem is:
Write a class named Book containing:

Two instance variables named title and author of type String.

A constructor that accepts two String parameters. The value of the first is used to initialize the value of title and the value of the second is used to initialize author .

A method named toString that accepts no parameters. toString returns a String consisting of the value of title , followed by a newline character, followed by the value of author .

And this is my response:

public class Book
{
 String title;
 String author;
  public Book(String x, String y)
   { title=x; author=y; }
   public String toString()
   {return title;
    return author;
    }
}

I want to know that is it ok to have two return statements in a single method? Because when I add the

return author;

to the method toString, the compiler returns a complain which says it's an unreachable statement.
Thank you very much!