java中的数字处理

//利用正则表达式来判断一个字符串是否是数字

import java.io.InputStream;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class 利用正则表达式来判断一个字符串是否是数字 {
	public static void main(String args[]) {
		Scanner s = new Scanner(System.in);
		String ss = s.next();
		String str="\\d{3,}";
		Pattern p =Pattern.compile(str);
		Matcher m = p.matcher(ss);
		while(m.find()){                          //找到一个向后跳的 
			System.out.print("LLLLMMMM****");
		}
	}
}
//3443jfkdfjkf4545545jkfjdkfjd34343jdkfjdkfjdkfj56566
//LLLLMMMM****LLLLMMMM****LLLLMMMM****LLLLMMMM****




public class 字符串转换为数字 {
	public static int convInt(String aa){
		return Integer.parseInt(aa);
	}
	public static int[] convIntArray(String str[]){
		if(str==null){return new int[0];}
		int ss[] = new int [str.length];
		for(int i=0;i<str.length;i++){
			ss[i]=convInt(str[i]);
		}
		return ss;
	}
	
	public static void main(String args[]){
		String s = "45679";
		//System.out.println(s+"字符串变为数字为："+convInt(s));
		String str[] ={"295","665","32","4"};
		int [] a =convIntArray(str);
		System.out.println("把str转换为整形数组后输出为：");
		for(int i=0;i<a.length;i++){
			System.out.print("   "+a[i]);
		}
		
		System.out.println("\n5的3次方是"+Math.pow(5, 3));
		System.out.println("100的平方根是："+Math.sqrt(100));
		System.out.println("5的平方根的整数值是："+Math.round(Math.sqrt(5)));
		
		
		
	}
	
}


import java.io.InputStream;
import java.util.Scanner;

public class 产生随机数 {
	public static void main(String args[]){
		System.out.println("猜字游戏！！！");
		int  guess = (int)MathRondom();
		int Num;
		boolean right = true;
		while(right){
			System.out.println("请你输入一个数：");
			Scanner s = new Scanner(System.in);
			Num=s.nextInt();
			System.out.println("你输入的数是"+Num);
			if(Num>guess){
				System.out.println("你输入的数大于这个数，请继续···");
			}
			else if(Num<guess){
				System.out.println("你输入的数小于这个数，请继续···");
			}
			else{
			System.out.println("恭喜你猜对了！！！");
			System.out.println("这个数是："+guess);
			right = false;
			}	
		}	
	}
	 
	public static double MathRondom(){
		double Mathtest = Math.random()*100;
		return Mathtest;
	}
}