用Java实现将一个字符串中的空格换成%20

package cn.com.cnn;

public class Replace {

    public String replaceMethod(String oldStr) {
        String newStr = oldStr.replace(" ", "%20");

        return newStr;
    }

    public String replaceMyMethod(StringBuffer oldStr) {
        int newStrLength = 0;
        int oldStrLength = 0;
        int spaceNumber = 0;
        StringBuffer newStr = new StringBuffer();
        System.out.println(newStr);
        for(int i = 0; i < oldStr.length(); i++) {
            oldStrLength++;
            newStr.append(" ");
            if(oldStr.charAt(i) == ' ') {
                spaceNumber++;
                newStr.append("  ");
            }
        }
        newStrLength = oldStrLength + 2 * spaceNumber;
        int indexOfOldStr = oldStrLength - 1;
        int indexOfNewStr = newStrLength - 1;
        for(int j = oldStrLength - 1; j >= 0; j--) {
            if(oldStr.charAt(j) != ' ') {
                newStr.setCharAt(indexOfNewStr--, oldStr.charAt(indexOfOldStr));
            } else {
                newStr.setCharAt(indexOfNewStr--, '0');
                newStr.setCharAt(indexOfNewStr--, '2');
                newStr.setCharAt(indexOfNewStr--, '%');
            }
            indexOfOldStr--;
        }

        return newStr.toString();
    }

    public static void main(String[] args) {
        String testString = "we are family";
        StringBuffer stringBuffer = new StringBuffer(testString);
        Replace replace = new Replace();
        System.out.println(replace.replaceMethod(testString));
        System.out.println(replace.replaceMyMethod(stringBuffer));

    }

}