Java代码输出菱形

import java.util.Scanner;


public class Student {

/**
 * @param args
 */
public static void main(String[] args) {
System.out.println("请输入行数：");
Scanner input=new Scanner(System.in);
int num=input.nextInt();
if(num%2==0){
//不能构成菱形
}else{
int n=(num+1)/2;
for(int i=1;i<=n;i++){
for(int j=1;j<=n-i;j++){
System.out.print(" ");
}
for(int k=1;k<=2*i-1;k++){
System.out.print("*");
}
System.out.println();
}
for(int i=n-1;i>=1;i--){
for(int j=1;j<=n-i;j++){
System.out.print(" ");
}
for(int k=1;k<=2*i-1;k++){