public String convert(int n){
    String s = "" + n;
    for(int i = s.length();i < 10;i++){
         s = '0' + s;
    }
    return s;
}

------解决方案--------------------
同问有简单的没？
Java code
import java.util.*;
public   class   test   {
public   static   void   main(String   args[]){
   Random rand=new Random();
   StringBuilder sb=new StringBuilder();
   String x;
   x=rand.nextInt(999999999)+"";
   int i=10-x.length();
   while(i>0){
       sb.append("0");
       i--;
   }
   sb.append(x);
   System.out.println(sb.toString());
}

}

------解决方案--------------------
import   java.util.*;  
public   class   compare  
{  
   public   static   void   main(String[]args)  
   {  
     S
   	System.out.println(new compare().getResult());
     }
     public Integer getLength(){
   	  Random ran = new Random();
   	 
   	  int len = ran.nextInt(10);
   	  return len;
     }
     public String getResult(){
   	  Random ran = new Random();
   	  String returnValue ="";
   	  int len =getLength();
   	  for(int i=1;i<=len;i++){
   		  Integer chara=ran.nextInt(10);
   		  returnValue+=chara.toString();
   	  }
   	  if(len<10)
   	  {
   		  returnValue="0000000000".substring(0,10-len)+returnValue;
   	  }
   	  return returnValue;
   	 
     }
}

------解决方案--------------------
import java.text.DecimalFormat;


public class Main {

	public static void main(String[] args)
	{
		int i = 3214561;
		DecimalFormat df = new DecimalFormat("0000000000");
		System.out.println(df.format(i));
	}
}
哦。不好意思。开始理解错了意思。原来不是要输出啊。那就用这个吧。。。

------解决方案--------------------
名有特色