Java missing return statement

The missing return statement is one of the most occurred errors in the Java program. The beginners usually face the missing return statement error. It is a compile-time error, it means that the error is raised when we compile program. The name of the error states the root cause of the error is that the return statement is missing in the program.

The Java missing return statement error mainly occurs due to human mistakes. It occurs when we use the return type before the method name and doesn't use the return statement. In Java, there can be two possible cases:

Method missing the return statement.
Missing return statement error within if / while / for.

Let's understand both the cases one by one.

Method missing the return statement

In this case, we will get the missing return statement when the method uses the return type but doesn't return any value. Let's take an example to understand the concept of missing return statement error in method.

MissingReturnStatementExample1.java

//import packages and classes
import java.util.*;
//create MissingReturnStatementExample1 for getting missing return statement error
public class MissingReturnStatementExample1 
{ 
	//create sum() method to find the sum of two numbers 
	public static int sum(int x, int y) {  
		//calculate sum 
		int z = x + y;
		//return sum of the numbers
		return z;
	}
	//create diff() method to find the difference of two numbers 
	public static int diff(int x, int y) {  
		
		//calculate difference
		int z = x - y;
		
		//throw missing return statement because it doesn't return an integer type value
	}
 
	public static void main(String args[]) {
		//get first and second number from the user using scanner class
		Scanner sc = new Scanner(System.in);
		System.out.print("Enter the first number: ");
		int x = sc.nextInt();
		
		System.out.print("Enter the second number: ");
		int y = sc.nextInt();
		
		//print the sum and the difference of the numbers
		System.out.println(sum(x, y));
		System.out.println(diff(x, y));
	}
}

Output

How to resolve the error?

There are two ways through which we can solve the error.

By using void return type
By adding a return statement

Both of these two ways are helpful only when we get this error in the method.

By using void return type

In the above code, we have created the diff() method in which we have declared return type as int. In this method, we didn't use the return statement, and due to which the diff() method throws the missing return statement. So, we will solve the problem by simply changing the return type to void without providing any return statement like as:

public static void diff(int x, int y) {  
	//calculate difference
	int z = x - y;
	//print the difference here instead of the main() method
	System.out.println(z);
}

Let's compile and run the above code.

By adding a return statement

Another way of resolving this error is simply adding the return statement to the method. We will return the difference of the numbers using the return keyword like:

public static int diff(int x, int y) {  
	//calculate difference
	int z = x - y;
	//return the difference of the number using the return statement
	return z;
}

The above program shows the following output.

Output:

Missing return statement error within if / while / for

The second case is quite different from the first case. In a method, when we use the return statement inside the if statement, or for loop or while loop but doesn't use the return statement at the end of the method, it throws the missing return statement error.

Let's take an example to understand it.

MissingReturnStatementExample2.java

//import packages and classes
import java.util.*;

//create MissingReturnStatementExample2 for getting missing return statement error
public class MissingReturnStatementExample2 
{	
	//create checkNumber() method to check the number 
    	public static String checkNumber( int number) {
        
		//initialize variable i
		int i = 0;
        
		//check whether the number is zero or not
		if (number == 0) {
            			return "It is not a valid number";
        		}
        
		//returning value in the for loop 
		for (i=0; i < number ;i++) { 
            			return "We are in the for loop";
        		}
        
		//returning value in the while loop 
		while (i < number) { 
            			return "We are in the while loop"; 
        		} 
        		//The method throws a missing return statement error   
     	}
   	public static void main(String args[]) {
        		//get number from the user using scanner class
		Scanner sc = new Scanner(System.in);
		System.out.print("Enter the first number: ");
		int x = sc.nextInt();
		
		//call checkNumber() method 
		System.out.println(checkNumber(x));
    	}
}

Output

How to resolve the error?

In order to solve the missing return statement error, we simply need to add the return statement to the method just like to the one we did in case one. So, we will return the some value of the same type which we used before the name like as:

public static String checkNumber( int number) {
	//initialize variable i
	int i = 0;
        	//check whether the number is zero or not
	if (number == 0) {
            		return "It is not a valid number";
        	}
        	//returning value in the for loop 
	for (i=0; i < number ;i++) { 
            		return "We are in the for loop";
        	}
	//returning value in the while loop 
	while (i < number) { 
            		return "We are in the while loop"; 
        	} 
	// adding return statement for the method
	return "number is valid";
     }

Let's compile and run the above program.

Output: