Program/Source Code:

The source code to convert the string into an enum constant is given below. The given program is compiled and executed successfully.

// Java program to convert the string 
// into an enum constant

public class Main {
  enum Vehicle {
    BIKE,
    CAR,
    BUS
  }

  public static void main(String[] args) {
    String str = "BUS";

    Vehicle v = Vehicle.valueOf(str);

    System.out.println(str);
  }
}

Output:

BUS

Explanation:

In the above program, we created an enumeration Vehicle inside class Main. The enum Vehicle contains 3 constants BIKE, CAR, BUS. The Main class also contains a static method main(). The main() method is the entry point for the program, here we created a string variable initialized with "BUS". Then we converted the string into an enum constant using the valueOf() method and printed the result.