C :

#include<stdio.h>
#include<string.h>
#include<ctype.h>

int main()
{
	int t,i;
	char a[51];
	scanf("%d%*c",&t);
	while(t--)
	{
		gets(a);
		for(i=0;i<strlen(a);i++)
		{
			if(a[i]=='A'||a[i]=='a'||a[i]=='E'||a[i]=='e'||a[i]=='I'||a[i]=='i'||a[i]=='O'||a[i]=='o'||a[i]=='U'||a[i]=='u')
				a[i]=toupper(a[i]);
			else
				a[i]=tolower(a[i]);
		}
		puts(a);
	}
	return 0;
}

Java :

import java.util.Scanner;

public class Main {
	
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		int t = in.nextInt();
		while(t-->0){
			String s = in.next();
			StringBuffer sb = new StringBuffer();
			for(int i=0;i<s.length();i++){
				char c = s.charAt(i);
				if(c>'Z'){
					if(c=='a'||c=='e'||c=='i'||c=='o'||c=='u')sb.append((char)(c-'a'+'A'));
					else sb.append(c);
				}else {
					if(c=='A'||c=='E'||c=='I'||c=='O'||c=='U')sb.append(c);
					else sb.append((char)(c-'A'+'a'));
				}
			}
			System.out.println(sb);
		}
	}
}