此方法必须返回boolean（Java）类型的结果

Question

this is my code.

boolean checkHit2() {
    if (cx < 0 || cx >= 640) {return true;}
    if (cy < ground[(int)cx]) {return false;}
    if (cx < blue + 15 && cx > blue - 15) {
        score = (int)score + 1;

What am I doing wrong? it gives me the error message "This method must return a result of type boolean". Please help.

Answer 1

"This method must return a result of type boolean"

Means your method should return the boolean value for every case . Currently it will return boolean if one of your if condition is true . What about if none of your if condition is true ? In this case compiler will not be able to return anything to the caller of the method. So that compiler is telling you to add a return statement for method for every case no matter condition satisfy or not. You should add return false at the end of the method.

Answer 2

In your method you must return a variable in each case (for each if statement), in this case, a boolean.

Example:

boolean checkHit2() {

  if (cx < 0 || cx >= 640) {return true;}
  if (cy < ground[(int)cx]) {return false;}
if (cx < blue + 15 && cx > blue - 15){
  score = (int)score + 1;
  return false;
}

Also, just to clean up your code a bit, the curly brackets are unneeded if the contents of the block is only one line. For example you can use:

boolean checkHit2() {

  if (cx < 0 || cx >= 640) return true;
  if (cy < ground[(int)cx]) return false;
if (cx < blue + 15 && cx > blue - 15){
  score = (int)score + 1;
  return false;
}

Functionally, they act the same. It's just a useful shortcut to clean up your code :).

In this example i simply returned false because i'm insure of the functionality of your program or how you would like it to work. You could return a value based on a if or else statement, etc. but it's up to you and what you want your program to do.

To see more about return , click here

Answer 3

This line:

<b>if (cx < blue + 15 && cx > blue - 15){ </b>

Should be changed to

<b>if((cx < (blue + 15)) && (cx > (blue -15))){</b>

but I think you should move the comparation out like:

int bluePlus = blue + 15;
int blueMinus = blue - 15;
if(cx < bluePlus && cx > blueMinus){

EDIT: The error means that you miss to return boolean after all. After the if

if(cx < bluePlus && cx > blueMinus){

then you need to add return to the result. Please ignore the first comment.