12-25判断是否是数值并格式化两位小数（四舍五入）

isNumber.java

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;
		}
	}

}