替换空格

题目：请事先一个函数，把字符串中的每个空格替换成“%20”。

import java.io.*;import java.util.*;public class exercise2 {	public static void main(String[] args) throws IOException {	//		Scanner s=new Scanner(System.in);	//		String line=s.nextLine();	   InputStream in=System.in;	   InputStreamReader isr=new InputStreamReader(in);	   BufferedReader bufr=new BufferedReader(isr);	   String line=null;	   while((line=bufr.readLine())!=null){					   int num=0;		   char[] c=line.toCharArray();		   for(int i=0;i<line.length();i++){			   if(c[i]==' ') num++;		   }		   System.out.PRintln(c.toString()+";");		   char newc[]=new char[c.length +num*2];		   int j=newc.length-1;		   int i = c.length-1;		   System.out .println(j);		   System.out .println(i);		   while(j>=0&&i>=0)		   {			   if(c[i]!=' '){				   newc[j--]=c[i--];			   }			   else{				   newc[j--]='0';				   newc[j--]='2';				   newc[j--]='%';				   i--;                }				   			}			   		   System.out.println(c);		   System.out.println(newc);		   }	   }		//别人的方法，将空格替换为任意的几个字符	    public static void repalce(char[] oldchar,char[] replacement){	        int sumOfSpace = 0;	        for(int i = 0;i < oldchar.length;i++){	            if(oldchar[i] == ' ')	                sumOfSpace++;	        }	        if(sumOfSpace == 0){	            return ;	        }	        char [] newchar = new char[oldchar.length + (replacement.length-1) * sumOfSpace];	        //指向被替换字符串的最后一个元素	        int pOld = oldchar.length - 1;	        //指向替换字符串的最后一个元素	        int pNew = newchar.length - 1;	        while(pNew >= 0){	            if(oldchar[pOld] == ' '){	                pOld--;	                for(int j = replacement.length - 1;j >= 0;j--){	                    newchar[pNew--] = replacement[j];	                }	            }else{	                newchar[pNew--] = oldchar[pOld--];	            }	        }	        for(char c:newchar){	            System.out.print(c);	        }	    }}