CODEWITHSUNDEEP
java
Bhavesh Jain
Bhavesh Jain

Reputation: 53

java.lang.Error: Unresolved compilation error: Unreachable code for loop

I had the following lines of code

boolean b = false;
for (int i = 0; b; i++) {}

it executes well

now if I replace above code with

for (int i = 0; false; i++) {}

it gives -> java.lang.Error: Unresolved compilation problem: Unreachable code

why? please help.

Upvotes: 0

Views: 2060

Answers (4)

Tarik
Tarik

Reputation: 11209

Sure! the loop body will never execute due to a false condition. As a result, the body of the loop and i++ is indeed unreachable. What's the point of doing that anyway?

Upvotes: 0

Rohit Jain
Rohit Jain

Reputation: 213331

Basically b in your first code is not a compile time constant expression, whereas false is. If you change the boolean variable in your first code to:

final boolean b = false;

it will too fail to compile, because now it's a constant expression, as value of b can't be changed later on.

Upvotes: 8

ssantos
ssantos

Reputation: 16536

Compiler won't complain if you use a variable for the condition as it doesn't check which value will have when execution reach the loop (that's a work for the runtime), as opposite to hardcode a false value.

Upvotes: 2

Jeroen Vannevel
Jeroen Vannevel

Reputation: 44448

The second parameter of your foreach loop is a condition. While this condition is true, the loop will execute. If you give false as the parameter, it will never execute and thus the code in it is unreachable.

The reason the first one works and the second doesn't is because the compiler didn't check the value (or can't sufficiently derive it) of b, yet when you plainly use false the condition is not ambiguous.

Upvotes: 4

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