1.5利用字符重复出现的次数，编写一个方法，实现基本的字符串压缩功能。如字符串aabcccccaaa会变成a2b1c5a3。若压缩后的字符串没有变短，则返回原字符串。

public String compressBad(String str)
{
    String mystr = "";
    char last = str.charAt(0);
    int count = 1;
    for (int i = 1; i < str.length(); i++)
    {
        if (str.charAt(i) = last)
        {
            count++;
        }
        else
        {
            mystr += last + "" + count;
            last = str.charAt(i)
            count = 1;
        }
    }
    return mystr + last + count;
}

String compressBetter(String str)
{
    int size = countCompression(str);
    if (size >= str.length())
    {
        return str;
    }
    
    StringBuffer mystr = new StringBuffer();
    char last = str.charAt(0);
    int count = 1;
    for (int i = 1; i < str.length(); i++)
    {
        if (str.charAt(i) == last)
        {
            count++;
        }
        else
        {
            mystr.append(last);
            mystr.append(ccount);
            last = str.charAt(i);
            count = 1;
        }
    }
    
    mystr.append(last);
    mystr.append(ccount);
    return mystr.toString();
}

//专门用来数长度
int countCompression(String str)
{
    if (str == null || str.isEmpty())
        return 0;
        
    char last = str.charAt(0);
    int size = 0;
    int count = 1;
    for (int i = 1; i <str.length(); i++)
    {
        if (str.charAt(i) == last)
        {
            count++;
        }
        else
        {
            last = str.charAt(i);
            size += 1 + String.valueOf(count).length();
            count = 1;
        }
    }
    size += 1 + String.valueOf(count).length();
    return size;
}