符号替换问题

public class ReplaceSpace {
　　// 问题:请实现一个函数，将一个字符串中的空格替换成“%20”。例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy。
    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);
        }
    }
}

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;
    }
}