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LL1.java
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LL1.java
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import java.util.Stack;
public class LL1
{
static Stack<String> myStack = new Stack<String>();
public boolean E(String token)
{
if(isInteger(token))
{
if(T(token))
newE(token);
}
switch(token)
{
case "+": return false;
case "*": return false;
case "(": token = myStack.pop();
if(T(token))
if(newE(token))
return true;
case ")": return false;
case "$": return false;
}
return true;
}
public boolean newE(String token)
{
if(isInteger(token))
return false;
switch(token)
{
case "+": myStack.push("+");
if(T(token))
if(newE(token))
return true;
case "*": return false;
case "(": return false;
case ")": myStack.pop();
break;
case "$": myStack.pop();
break;
}
return true;
}
public boolean T(String token)
{
if(isInteger(token))
{
if(F(token));
newT(token);
}
switch(token)
{
case "+": return false;
case "*": return false;
case "(": token = myStack.pop();
if(F(token))
if(newT(token))
return true;
case ")": return false;
case "$": return false;
}
return true;
}
public boolean newT(String token)
{
if(isInteger(token))
return false;
switch(token)
{
case "+": myStack.pop();
break;
case "*": myStack.push("*");
if(F(token))
if(newT(token))
return true;
case "(": return false;
case ")": myStack.pop();
break;
case "$": myStack.pop();
break;
}
return true;
}
public boolean F(String token)
{
if(isInteger(token))
{
myStack.push(token);
return true;
}
switch(token)
{
case "+": return false;
case "*": return false;
case "(": token = myStack.pop();
if(E(token))
myStack.push(")");
case ")": return false;
case "$": return false;
}
return true;
}
public boolean isInteger(String token)
{
try
{
Integer.parseInt(token);
return true;
}
catch(Exception e)
{
return false;
}
}
public static void main(String [] args)
{
LL1 test = new LL1();
String input = "123+((23+2*3)))+3";
String [] result = input.split("(?!^)");
for(int i = 0; i<result.length; i++)
myStack.push(result[i]);
for(int i=0; i<result.length; i++)
{
if(test.E(myStack.pop()))
System.out.println(result[i] + " is okay!");
else
System.out.println(result[i] + " is incorrect!");
}
}
}