157.用Read4读取N个字符

/**
 * The read4 API is defined in the parent class Reader4.
 *     int read4(char[] buf4);
 */

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) {
        //int read4(char[] buf)。根据定义，方法 read4 每次读取 k 个字符（k 不超过 4），并将读取的字符存入其输入参数 buf 中
        int index = 0;
        char[] tmp = new char[4];
        while(index < n){
            int count = read4(tmp);
            if(count == 0){
                break;
            }
            for(int i = 0; i < count ;i++){
                buf[index+i] = tmp[i];
            }
            index+=count;
        }
        return Math.min(index,n);
    }
}