How to Convert String to int in Java?

public class StudyTonight
{  
    public static void main(String args[])
    {  
        String s = "454"; //String Declaration 
        System.out.println("String value "+s);  
        int i = Integer.parseInt(s);
        System.out.println("Integer value "+i);  
    }
} 

public class StudyTonight
{  
    public static void main(String args[])
    {    
        try
        {
            String s1 = "500"; //String declaration 
            Integer i1 = Integer.valueOf(s1);  // Integer.valueOf() method converts a String into Integer
            System.out.println(i1);  

            String s2 = "mohit"; //NumberFormatException
            Integer i2 = Integer.valueOf(s2);
            System.out.println(i2);        
        }
        catch(Exception e)
        {
            System.out.println("Invalid input");
        }
    }
}

class StudyTonight
{
    public static int strToInt(String str)
    {
        int i = 0;
        int num = 0;
        boolean isNeg = false;

        // Check for negative sign; if it's there, set the isNeg flag
        if (str.charAt(0) == '-') 
        {
            isNeg = true;
            i = 1;
        }

        // Process each character of the string;
        while( i < str.length())
        {
            num *= 10;
            num += str.charAt(i++) - '0'; // Minus the ASCII code of '0' to get the value of the charAt(i++).
        }

        if (isNeg)
            num = -num;
        return num;
    }
    public static void main(String[] args)
    {
        String s = "45734";
        int i = strToInt(s);
        System.out.println("Int value is : "+i);
    }
}