12-25判断是否是数值并格式化两位小数（四舍五入）

import java.io.InputStream;

public class isNumber {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String str="1209.3357";
if(isNum(str)){
System.out.println("是数值");
double str1=Double.parseDouble(str);
System.out.println(reNum(str1));
}else{
System.out.println("不是数值");
}

}
public static boolean isNum(String str){
int count=0;
for(int i=0;i<str.length();i++){
char ac=str.charAt(i);
if(!(ac>='0'&&ac<='9'||ac=='.')){
return false;
}
if(ac=='.'){
count++;
}
}
if(count>1){
return false;
}
return true;
}
public static String reNum(double num){
String str=num+"";
String s1=str.substring(str.indexOf(".")+1);
if(s1.length()==1){
return str+"0";
}else if(s1.length()>2){
num=(int)(num*100+0.5)/100.0;
return reNum(num);
}else{
return str;
}
}

}