去字符串中的0

//去掉字符串前面的0
String str = "000000021";
String newStr = str.replaceAll("^(0+)", "");
System.out.println(newStr);

result = 21


//去掉字符串后面的0
String str = "2100000";
String newStr = str.replaceAll("0*$", "");
System.out.println(newStr);

result = 21