157. Read N Characters Given Read4

/**
 * The read4 API is defined in the parent class Reader4.
 *     int read4(char[] buf);
 */
public class Solution extends Reader4 {
    /**
     * @param buf Destination buffer
     * @param n   Number of characters to read
     * @return    The number of actual characters read
     */
    public int read(char[] buf, int n) {
        boolean endOfFile = false;
        int i = 0;
        while (i < n && !endOfFile) {
            char[] temp = new char[4];
            int read4 = read4(temp);
            if (read4 != 4) {
                endOfFile = true;
            }
            int len = Math.min(read4, n - i);
            for (int j = 0; j < len; j++) {
                buf[i++] = temp[j];
            }
        }
        return i;
    }
}