Leetcode-Read N Characters Given Read4

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 will only be called once for each test case.

Solution:

/* 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   Maximum number of characters to read
     * @return    The number of characters read
     */
    public int read(char[] buf, int n) {
        char[] tempBuf = new char[4];
        int left = n;
        while (left>0){
            int num = read4(tempBuf);
            //if the read number is larger then what we need, then we just put the left number of chars into buf.
            int end = Math.min(num,left);
            for (int i=0;i<end;i++){
                buf[n-left] = tempBuf[i];
                left--;
            }
  
            //If reach EOF.
            if (left>0 && num<4) break;
        }
         
        return n-left;   
        
    }
}