Java，程序

import java.util.*;
public class Test{

public static void main(String[] args){
Scanner sc = new Scanner(System.in);
double x = sc.nextDouble();
if(x<1) System.out.println(x);
if(x>=10)System.out.println(4*x);
else System.out.println(3*x-2);
}
}

呃。。刚才有点小问题，呵呵。。

package idle;

import java.util.Scanner;

public class A {

public static int cal(int x){
if(x < 1)
return x;
else if(x >= 10)
return 4 * x;
else
return 3 * x - 2;
}

public static void main(String[] args) {
System.out.println("Please input x:");
Scanner scanner = new Scanner(System.in);
try{
int x = scanner.nextInt();
System.out.println(A.cal(x));
}catch(Exception e){
e.printStackTrace();
}
}

}

没想到silentplay已经贴出来了，呵呵
他答的不错，简洁漂亮。