Java Program to Check whether an expression is valid or not

//Expression validity check.

import java.util.*;

class ExpValidityCheck

{

public void check_Validity(String str)

{

int i=0,c=0,operand=0,operator=0,flag=1;

char ch;

for(i=0;i<str.length();i++)

{

ch=str.charAt(i);

if(ch>='A' && ch<='Z')

{

if(str.charAt(i+1)>='A' && str.charAt(i+1)<='Z')

{

flag=0;

break;

}

else

operand++;

}

else if((ch=='+')||(ch=='-')||(ch=='*')||(ch=='/')||(ch=='%'))

operator++;

else if(ch=='(')

{char ch1=str.charAt(i+1);

if((ch1=='+')||(ch1=='-')||(ch1=='*')||(ch1=='/')||(ch1=='%'))

{ flag=0;

break;

}

c++;

}

else if(ch==')')

{

c--;

if(c<0)

{

flag=0;

break;

}

char ch1=str.charAt(i-1);

if((ch1=='+')||(ch1=='-')||(ch1=='*')||(ch1=='/')||(ch1=='%'))

{ flag=0;

break;

}

}

}

if(flag==1)

{

if(operator + 1==operand)

System.out.println("Valid expression");

else

System.out.println("Invalid expression");

}

else

System.out.println("Invalid expression");

}

}