Optimizing an expression of the form:

(a() || true)

to true is wrong if a() can raise an exception. Related JLS sections: 15.23
(definition of ||), 14.8 (definition of if stmt), 15.5 (definition of
abrupt completion of evaluation -- see also example on top of page 307).

The following program should not produce any output, but does:

public class Test {
public static void main(String args[]) throws Exception {
if (foo() || true) {
System.out.println("You shouldn't see this line");
}
}
 
public static boolean foo() throws Exception {
throw new Exception();
}
}

"javap -c Test" clearly shows that javac just short-circuited the call to
foo() in main() and called println directly. See ---> lines.

$ javap -c Test
        Compiled from Test.java
        public synchronized class Test extends java.lang.Object
            /* ACC_SUPER bit set */
        {
            public static void main(java.lang.String[]);
            public static boolean foo();
            public Test();
        }
 
        Method void main(java.lang.String[])
---> 0 getstatic #9 <Field java.io.PrintStream out>
---> 3 ldc #1 <String "You shouldn't see this line">
---> 5 invokevirtual #10 <Method void println(java.lang.String)>
           8 return
 
        Method boolean foo()
           0 new #4 <Class java.lang.Exception>
           3 dup
           4 invokespecial #7 <Method java.lang.Exception()>
           7 athrow
 
        Method Test()
           0 aload_0
           1 invokespecial #8 <Method java.lang.Object()>
           4 return