Result of a method

1. The return statement

Think you've already learned all about Java methods? Whatever you think you know, you still don't know the half of it.

Let's start with something simple. For example, Java has a return statement that lets you instantly terminate the method that calls it. Here's the statement:

return;

It's simple: the solitary word return followed by a semicolon. As soon as the program executes this statement, the current method exits immediately, and the calling continues.

If return is called in the main method, then the main method will immediately end, and with it the entire program.

Example:

class Solution
{
   public static void fill(int[] data, int from, int to, int value)
   {


     if (from < 0 || to > data.length)
       return;

     for (int i = from; i < to; i++)
     {
       data[i] = value;
     }
   }

   public static void main(String[] args)
   {
     int[] months = {1, 2, 3, 4, 5, 6, 7, 8 ,9, 10, 11, 12};
     fill(months, 2, 10, 8);
   }
}

The above program has a fill method that fills the array passed to it with value. It does not fill the entire array, only the part specified by the indices from and to.

At the beginning of the fill method, the passed values are checked to ensure that they are valid. If from is less than 0, or if to is greater than the length of the array, then the fill method terminates immediately (executes a return statement).

This return statement is useful: practically every method in Java has one, and here's why.

9

Task

New Java Syntax, level 9, lesson 2

Locked

Octal converter

The public static toOctal(int) method must convert the integer received as an input parameter from the decimal numeral system into octal. And conversely, the public static toDecimal(int) method converts from the octal system into decimal. The methods only work with positive numbers. If the input par

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2. Methods with a result, void

Remember we once figured out that there are statements, and there are expressions. An expression, unlike a statement, has a value that can be used somewhere.

And, in Java, methods can have a value. And this is very good news: methods are not only able to do something based on the input parameters, but also, for example, to evaluate something and return the result of the calculation.

By the way, you have already encountered such methods:

double delta = Math.abs(d1 - d2);

Scanner console = new Scanner(System.in);
int x = console.nextInt();

String str = "Hello";
String s2 = str.toUpperCase();

int[] data = {1, 4, 5, 6, 7, 8, 11};
int[] array = Arrays.copyOf(data, 4);

Each method can only return one value of one predetermined type. The return type is determined when the method is declared:

public static Type name(parameters)
{
  method body
}

Where name is the name of the method, parameters is the list of method parameters, and type is the type of the result that the method returns.

For methods that return nothing, there is a special placeholder type: void.

Are you writing your own method and don't want to return anything to the calling method? Just declare the method's type as void, and the problem is solved. There are also lots of methods like this in Java.

3. Returning a result

We just figured out how to declare a method that returns the result of a calculation, but how do we result this result in the method itself?

The return statement helps us out here once again. Passing a result from a method looks like this:

return value;

Where return is a statement that terminates the method immediately. And value is the value that the method returns to the calling method when it exits. The type of value must match the type specified in the method declaration.

Example 1. The method calculates the minimum of two numbers:

int min(int a, int b)
{
   if (a < b)
     return a;
   else
     return b;
}

Example 2. The method duplicates the string passed to it n times:

String multiple(String str, int times)
{
   String result = "";
   for (int i = 0; i < times; i++)
     result = result + " "+ str;
   return result;
}

Example 3: The method calculates the maximum of two numbers using the ternary operator:

int max(int a, int b)
{
   return (a > b ? a : b);
}

9

Task

New Java Syntax, level 9, lesson 2

Locked

Binary converter

The public static toBinary(int) method must convert the integer received as an input parameter from the decimal numeral system to binary and return its string representation. And conversely, the public static toDecimal(String) method converts from the string representation of a binary number to a de

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9

Task

New Java Syntax, level 9, lesson 2

Locked

Hexadecimal converter

The public static toHex(String) method must convert the integer received as an input parameter from the decimal numeral system to hexadecimal and return its string representation. And conversely, the public static toDecimal(String) method converts from the string representation of a hexadecimal numb

Open

9

Task

New Java Syntax, level 9, lesson 2

Locked

Binary to hexadecimal converter

The public static toHex(String) method must convert the string representation of a binary number, received as an input parameter, from the binary numeral system to hexadecimal and return its string representation. And conversely, the public static toBinary(String) method converts from the string rep

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