for loop not compiling

[mvPrasad Regula]

public class Temp
{
public static void main(String[] args)
{
int i = 0;
for ( ; i<10; i++) ; // (1)
System.out.println("1= "+i);
for (i=0; ; i++) break; // (2)
System.out.println("2= "+i);
for (i=0; i<10; ) i++; // (3)
System.out.println("3= "+i);
for ( ; ; ) ; // (4)
System.out.println("4= ");
}
}

When I compile javac Temp.java, I get an error For the fourth System.out.println as "statement unreachable". Has it been at runtime I can consider that the fourth for loop is an infinite so the System.out.println is unreachable. This is compile time error.

[mvPrasad Regula]

It has been changed

[Henry Wong]

Has it been at runtime I can consider that the fourth for loop is an infinite so the System.out.println is unreachable. This is compile time error.

The compiler has logic to detect, under certain conditions, if code is unreachable. In this case, it can detect that the fourth for-loop is an infinite loop.

Henry

[Atwal Usha]

Hi,

As the for loop at line no. 4 is an endless loop so compiler will never be able to reach any statement after that for the compilation purpose and therefore an error is thrown stating it to be an unreachable statement.

[Harsh Pensi]

Can you give some more examples of such non-trivial issues where the compiler IMO behaves over-smart??? Got my exam on Monday and still new things coming up

[Ankit Garg]

I think that in some cases the compiler is not smart enough to detect something leaving aside being oversmart.

int i;
if(true) {
    i = 10;
}
else {
    System.out.println("never reached");
}
System.out.println(i);

Here the compiler detects that i is initialized but doesn't give an error that the else part is unreachable...

[Harsh Pensi]

Also, compiler gives Unreachable code error with while(false){}, but not with if(false){}.

[KrishnaPrasad raghavan]

Just Remove the ; after the for( ; ; ) ;. I am sure the compiler won't complain.

[Siva Masilamani]

Visit this link to get some idea about compile time resolution

Compile time constant