157. 用 Read4 读取 N 个字符(仅java ac代码

 

/**
 * 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 ans = 0;
        char[] buf4 = new char[4];//目标缓存区
        int size = read4(buf4);
        while(size>0&&ans<n){
            //size>0指的是文件还有剩余的字符
            //ans<n意思就是目前的长度不超过n
            for(int i=0;i<size&&ans<n;++i){
                buf[ans++] = buf4[i];
            }
            size = read4(buf4);
        }
        return ans;
    }
}