Authors:
Michael T. Goodrich, Roberto Tamassia, Michael H. Goldwasser
Chapter:
Object-oriented Design
Exercise:
Exercises
Question:17 | ISBN:9781118771334 | Edition: 6
Question
Most modern Java compilers have optimizers that can detect simple cases when it is logically impossible for certain statements in a program to ever be executed. In such cases, the compiler warns the programmer about the useless code. Write a short Java method that contains code for which it is provably impossible for that code to ever be executed, yet the Java compiler does not detect this fact
Answer
package Data_Structures.Chapter2;
public class DeadCode {
// this method has unreachable code and gives compilation error if we uncomment the println statement
public void thisMethodHasUnreachableCode() {
System.out.println("Reachable code");
return;
// below line cause compilation problem as it is unreachable code
// System.out.println("Unreachable code");
}
// below method has deadcode it wont cause compilation error, but gives waring
public void thisMethodHasDeadCode() {
System.out.println("Reachable code");
if (2 < 3) {
return;
}
System.out.println("Dead Code");
}
// this method too has unreachable code and gives compilation error if we uncomment the println statement
public void thisOneHasUnreachableCode() {
System.out.println("Reachable code");
while (1 < 2) {
return;
}
// System.out.println("Again unreachable code");
}
public static void main(String args[]) {
DeadCode deadcode = new DeadCode();
deadcode.thisMethodHasUnreachableCode();
deadcode.thisMethodHasDeadCode();
deadcode.thisOneHasUnreachableCode();
}
}
Output:
Reachable code
Reachable code
Reachable code