Read N Characters Given Read4 II - Call multiple times leetcode

The API: int read4(char *buf) reads 4 characters at a time from a file.

The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the file.

By using the read4 API, implement the function int read(char *buf, int n) that reads n characters from the file.

Note:
The read function may be called multiple times.

/* The read4 API is defined in the parent class Reader4.
      int read4(char[] buf); */

public class Solution extends Reader4 {
    Queue queue = new LinkedList();
    public int read(char[] buf, int n) {
        int i = 0;
        while (i < n && !queue.isEmpty()) {
            buf[i] = queue.poll();
            i++;
        }
        for (; i < n; i+= 4) {
            char[] tem = new char[4];
            int len = read4(tem);
            if (len > n - i) {
                System.arraycopy(tem, 0, buf, i, n - i);
                for (int j = n - i; j < len; j++) {
                    queue.offer(tem[j]);
                }
            } else {
                System.arraycopy(tem, 0, buf, i, len);
            }
            if (len < 4) {
                return Math.min(len + i, n);
            }
        }
        return n;
    }
}