Robot Bounded In Circle

On an infinite plane, a robot initially stands at (0, 0) and faces north. The robot can receive one of three instructions:

• "G": go straight 1 unit;

• "L": turn 90 degrees to the left;

• "R": turn 90 degress to the right.

The robot performs the instructions given in order, and repeats them forever.

Return true if and only if there exists a circle in the plane such that the robot never leaves the circle.

Example 1:

Input: "GGLLGG"
Output: true
Explanation: 
The robot moves from (0,0) to (0,2), turns 180 degrees, and then returns to (0,0).
When repeating these instructions, the robot remains in the circle of radius 2 centered at the origin.

Example 2:

Input: "GG"
Output: false
Explanation: 
The robot moves north indefinitely.

Example 3:

Input: "GL"
Output: true
Explanation: 
The robot moves from (0, 0) -> (0, 1) -> (-1, 1) -> (-1, 0) -> (0, 0) -> ...

Note:

1. 1 <= instructions.length <= 100

2. instructions[i] is in {'G', 'L', 'R'}

class Solution {
    public boolean isRobotBounded(String instructions) {
        int xCurr = 0, yCurr = 0, xDir = 0, yDir = 1;
        while (true) {
            for (char c : instructions.toCharArray()) {
                if (c == 'G') {
                    xCurr += xDir;
                    yCurr += yDir;
                } else if (c == 'L') {
                    if (xDir == 0 && yDir == 1) {
                        xDir = -1;
                        yDir = 0;
                    } else if (xDir == -1 && yDir == 0) {
                        xDir = 0;
                        yDir = -1;
                    } else if (xDir == 0 && yDir == -1) {
                        xDir = 1;
                        yDir = 0;
                    } else {
                        xDir = 0;
                        yDir = 1;
                    }
                } else {
                    if (xDir == 0 && yDir == 1) {
                        xDir = 1;
                        yDir = 0;
                    } else if (xDir == -1 && yDir == 0) {
                        xDir = 0;
                        yDir = 1;
                    } else if (xDir == 0 && yDir == -1) {
                        xDir = -1;
                        yDir = 0;
                    } else {
                        xDir = 0;
                        yDir = -1;
                    }
                }
            }
            if (xDir == 0 && yDir == 1) {
                if (xCurr == 0 && yCurr == 0)
                    return true;
                break;
            }
        }
        return false;
    }
}