Convert a given 12 hour time to its equivalent 24 hour time form?

import java.util.*;
public class Main
{
static void print24(String a)
{
char x[]=a.toCharArray();
int n=a.length();
if(x[n-2]=='A')
{
if(x[0]=='1' && x[1]=='2')
{
x[0]='0';
x[1]='1';
}
}
else
{
if(!(x[0]=='1' && x[1]=='2'))
{
int t=(x[0]-48)*10+(x[1]-48)+12;
x[1]=(char)((t%10)+48);
x[0]=(char)((t/10)+48);
}
}
System.out.print(new String(x).substring(0,n-2));
}
public static void main(String[] args)
{
Scanner s=new Scanner(System.in);
String str=s.nextLine();
print24(str);
}
}