I am a new-comer to the java language, and I'm confused as to why I am getting an error here. It's a very short piece of code that I seem to have a mental block about. Any suggestions?
public class Rigidbody {
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
if(Math.sqrt(((x2-x1)^2)+((y2-y1)^2))<=(size1+size2)){
return true;
}
}
}
Does anyone know what I'm missing here? (It's probably really obvious).
Well, firstly, you forgot to have an else clause:
public boolean checkCircleCollision(float x1, float y1, float r1,
float x2, float y2, float r2) {
if (Math.sqrt(((x2 - x1) ^ 2) + ((y2 - y1) ^ 2)) <= (r1 + r2)){
return true;
} else {
return false;
}
}
Someone else already pointed out this can be shortened as follows:
public boolean checkCircleCollision(float x1, float y1, float r1,
float x2, float y2, float r2) {
return Math.sqrt(((x2 - x1) ^ 2) + ((y2 - y1) ^ 2)) <= (r1 + r2);
}
(make sure to upvote them for pointing those out :-)
However, your code is still wrong.
As stated here, Java's ^ operator is for exclusive bitwise OR, not exponentiation. Perhaps you want Math.pow()?
Returns the value of the first argument raised to the power of the second argument.
public boolean checkCircleCollision(float x1, float y1, float r1,
float x2, float y2, float r2) {
return Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2)) <= (r1 + r2);
}
Or, you can also just use Math.hypot rather than rolling your own!
Returns sqrt(x^2 + y^2) without intermediate overflow or underflow.
public boolean checkCircleCollision(float x1, float y1, float r1,
float x2, float y2, float r2) {
return Math.hypot(x2 - x1, y2 - y1) <= (r1 + r2);
}
You can make the method's body much simpler...
public class Rigidbody {
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
return Math.sqrt(((x2-x1)^2)+((y2-y1)^2))<=(size1+size2)
}
}
The result of <= is always a Boolean.
You forgot the else part of the if.
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
if (Math.sqrt(Math.pow(x2-x1, 2)+ Math.pow(y2-y1,2)) <= (size1+size2)) {
return true;
} else {
return false;
}
}
Which can be simplified to:
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
return Math.sqrt(Math.pow(x2-x1, 2)+ Math.pow(y2-y1,2)) <= (size1+size2);
}
EDIT: Also, as noted by @veer, you are using ^2 when you should be using Math.pow, since the ^ operator in Java is a bitwise XOR, not the power operator. So go upvote and accept his answer, as that is the main cause of the error.
OP has a problem in his/her code due to the ^ symbol usage that should be replaced by Math#pow(), good point every one! But he/she's asking what its missing. The answer is very simple: every method must return a value, except for void methods.
If you have
public boolean aBooleanMethod(int x) {
//some fancy and nice code!
return true;
}
The compiler will be happy. But, if you do something like this:
public boolean anotherBooleanMethod(int x) {
if (x < 2) {
return true;
}
}
The compiler will throw an exception:
This method must return a result of type boolean.
Why is this? Because at the end of the method, the compiler find a path that could not return a value, so instead of make your program crash or return an unexpected result (like false when there is no return associated), the Java compiler will throw the exception.
How to solve it? Easy: don't forget to return a value on every path in your method.
Ways to solve the problem in the last piece of code:
Adding a default return at the end of the method. This is a common approach used by almost all programmers.
public boolean anotherBooleanMethod(int x) {
if (x < 2) {
return true;
}
//if the method has never returned true, then it must return false...
return false;
}
For boolean results, you can return a condition:
public boolean anotherBooleanMethod(int x) {
//your method always return a value, no compiler problems
//the value depends if x is less than 2 (true) or 2 or more (false)
return (x < 2);
}
About the exception of the void methods, this doesn't mean that a void method can't use the return keyword, just means that it must return "nothing". To post a sample:
public void theVoidMethod(int x) {
System.out.println("Welcome to theVoidMethod!");
if (x < 2) {
//return nothing! End of the method
return;
}
System.out.println("You've reached the bottom of theVoidMethod!");
//here, the Java compiler will add a return sentence for you, no need to code it
//return
}
If you test this method using 1 and 2 as parameters you will get different results:
theVoidMethod(1):
Welcome to theVoidMethod!
theVoidMethod(2):
Welcome to theVoidMethod!
You've reached the bottom of theVoidMethod!
Now, to solve another problems in your code, you should use the Math#pow method instead of ^ symbol, but that's heavily explained in the other answers.
Try this, I have used Math.pow for the square. Also added return statement for the else condition.
public class Rigidbody {
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
return (Math.sqrt(Math.pow((x2-x1), 2) + Math.pow((y2-y1), 2)) <= (size1+size2));
} }
when that condition false it not return any thing that's why it wrong.
public class Rigidbody {
public boolean checkCircleCollision(float x1,float y1,float size1,float x2,float y2,float size2){
if(Math.sqrt(((x2-x1)^2)+((y2-y1)^2))<=(size1+size2)){
return true;
}
else{
return false
}
}
}
ifcondition is not satisfied so, in else part you need to return else. For these type of coding its better to useflags.