Can someone please explain to me why I’m receiving the above error message? Thanks
// Import statement:
import java.util.ArrayList;
class PrimeDirective {
// Add your methods here:
public boolean isPrime(int number) {
if (number >= 2) {
return true;
} else if (number < 2){
return false;
}
for (int i = 2; i < number; i++) {
if (number % i == 0) {
return false;
} else if (number % i != 0){
return true;
}
}
}
public static void main(String[] args) {
PrimeDirective pd = new PrimeDirective();
int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
}
}
In Java all paths must eventually lead to a return. In the event that none of your if or else if conditions evaluate to truthy, there is no default return. The compiler only sees that every return is conditional.
I’ve made a few tweeks to both if else statements, and I’m still getting the same error message. Where am I missing a return statement please?
import java.util.ArrayList;
class PrimeDirective {
// Add your methods here:
public boolean isPrime(int number) {
if (number >= 2) {
return true;
} else if (number < 2){
return false;
} else {
System.out.println("Error");
}
for (int i = 2; i < number; i++) {
if (number % i == 0) {
return false;
} else if (number % i != 0){
return true;
} else {
return false;
}
}
}
public static void main(String[] args) {
PrimeDirective pd = new PrimeDirective();
int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
}
}
You need a return true outside the loop and outside any if or else-if or else blocks, at the end of the function, so the compiler has something to return (and it that be true, so that if no factors/divisors were found, you have true for being prime).
Some of the other returns in the code are not necessary:
the return in the else-if block and the return in the else block should not be there
because you want the loop to keep going even if the first number it checks for i (which is 2) is not a factor of number.
(By factor or divisor of number, I mean something that divides number evenly into an integer, so the remainder would be 0.)
The compiler is complaining that you don’t have a return that is guaranteed to be reached. All of your return statements are only reached based on a condition evaluating to truthy. Consider the following.
Example:
public class IsMe {
public boolean isMe(String n) {
if( n == "Tod") {
return true;
} else if (n != "Tod") {
return false;
}
}
public static void main(String[] args) {
IsMe iM = new IsMe();
System.out.println(iM.isMe("Tod"));
}
}
Try compiling:
$ javac IsMe.java
IsMe.java:8: error: missing return statement
}
^
1 error
$
Two ways to fix:
Either:
public class IsMe {
public boolean isMe(String n) {
if( n == "Tod") {
return true;
} else {
return false; //No condition. If the above return isn't reached, this one will be for sure.
}
}
public static void main(String[] args) {
IsMe iM = new IsMe();
System.out.println(iM.isMe("Tod"));
}
}
Try compiling & executing:
$ javac IsMe.java
$ java IsMe
true
$
Or using a default return:
public class IsMe {
public boolean isMe(String n) {
if( n == "Tod") {
return true;
}
return false; //default return
}
public static void main(String[] args) {
IsMe iM = new IsMe();
System.out.println(iM.isMe("Larry"));
}
}
Try compiling & executing:
$ javac IsMe.java
$ java IsMe
false
$
I need some help with this project as well. I wrote my code like this:
import java.util.ArrayList;
class PrimeDirective {
// Add your methods here:
public boolean isPrime(int number){
if (number == 2){
return true;
}
else if (number < 2){
return false;
}
for (int i = 2; number < 2; i++){
if (number % 1 == 0){
return false;
}
}
return true;
}
public static void main(String args) {
PrimeDirective pd = new PrimeDirective();
int[] numbers = {6, 29, 28, 33, 11, 100, 101, 43, 89};
System.out.println(pd.isPrime(7));
System.out.println(pd.isPrime(28));
System.out.println(pd.isPrime(2));
System.out.println(pd.isPrime(0));
}
}
the problem is when i try to run the code is come out with true true true false.
when 28 should come out to be false.
Did i code something wrong>
Your for-loop and the if-statement in it has the wrong conditions …
You need to check if there’s any integer i below number that id a divisor/factor for number.
Also, every integer is divisible by 1, so number % 1 == 0 will always be true.
Instead this should be number % i == 0 to see if there’s a remainder of 0 when you divide by different values for i
to check whether i is a factor of number.
for (int i = 2; i < number; i++){
if (number % i == 0){
return false;
}
}
1 Like
Thanks you! Yea I found my mistake after i posted that lol But thank you for the help!