[Leetcode] zigzag Conversion

The string"PAYPALISHIRING"Is written in a zigzag pattern on a given number of rows like this: (You may want to display this pattern in a fixed font for better legibility)

P   A   H   NA P L S I I GY   I   R

And then read line by line: "PAHNAPLSIIGYIR"

Write the code that will take a string and make this conversion given a number of rows:

string convert(string text, int nRows);

convert("PAYPALISHIRING", 3)Shocould return"PAHNAPLSIIGYIR".

public class Solution {    public String convert(String s, int nRows) {    if(nRows==1||s.length()<=nRows){    return s;    }    StringBuffer sb=new StringBuffer();    for(int i = 0;i<nRows;i++){    if(i==0||i==nRows-1){    for(int j=0;i+j<s.length();j+=2*(nRows-1)){    sb.append(s.charAt(i+j));    }    continue;    }    int k=0;    for(int j = i;j<s.length();){    if(k==0){    sb.append(s.charAt(j));    k++;    continue;    }    if(k%2!=0){    j+=2*(nRows-i-1);    if(j>=s.length()) break;    sb.append(s.charAt(j));    k++;    }else{    j+=2*i;    if(j>=s.length()) break;    sb.append(s.charAt(j));    k++;    }    }    }    return sb.toString();    }}