public class Solution {    public String replaceSpace(StringBuffer str) {        String str1=str.toString();        char[] charArray = str1.toCharArray();        StringBuilder sBuilder = new StringBuilder();        for (char c : charArray) {            if(c==' ') {            sBuilder.append("%20");                }else {                sBuilder.append(c);            }        }        String string = sBuilder.toString();        return string;    }}

import java.util.Scanner;public class ReplaceSpace {    public static void main(String[] args) {        Scanner scanner = new Scanner(System.in);        String str=scanner.nextLine();        scanner.close();        char[] charArray = str.toCharArray();        int length=charArray.length;        int spaceNumber=0;//获取空格数量        for (char c : charArray) {            if(c==' ') {            spaceNumber++;            }        }        int newLength=length+spaceNumber*2;        char[] tempArray=new char[newLength];//新的数组的长度        System.arraycopy(charArray, 0, tempArray, 0, length);//将原来的数组拷贝到新长度的数组中        int indexofOriginal = length - 1;          int indexofNew = newLength - 1;          while (indexofOriginal>=0&&indexofOriginal!=indexofNew) {            if (tempArray[indexofOriginal]==' ') {                tempArray[indexofNew--] = '0';                 tempArray[indexofNew--] = '2';                tempArray[indexofNew--] = '%';            }else {                tempArray[indexofNew--] = tempArray[indexofOriginal];            }            indexofOriginal--;                    }        for (char c : tempArray) {            System.out.print(c);        }    }}