What's the different between consecutive if and nested if?

I am new to Java. Here are my two codes.

1).

---

    if (!isCorrectGuess(guess) && !isPriorGuess(guess)){
        state += 1;
    }

    if( isCorrectGuess(guess) && !isPriorGuess(guess)){
        correctguess += guess;
    }

    if (!isPriorGuess(guess)){
        guessed += guess;
    }

    return isCorrectGuess(guess) && !isPriorGuess(guess);

2).

---

    if (!isPriorGuess(guess)){
        guessed += guess;
        if (isCorrectGuess(guess)){
            correctguess += guess;
            return true;
        }
        else{
            state += 1;
            return false;
        }
    }
    return false;

I think they should have the same result, but it seems I am wrong. Could anyone tell my what's the difference between the two codes? Thanks!