Java Notes

01) Java notes

Java working notes about important points 

02) Manipulate Strings

    // Create char array from String
    
    char[] charArray = str.toCharArray();  => string to char array 
    char[] reversedArray = new char[charArray.length]; => create new char array ( str.length() can use instead charArray.length )
    
    ***************************************************
    
    // Using mutable StringBuilder class instead immutable String class when manipulate String  
    
    StringBuilder builder_str = new StringBuilder(str);
    String reversed_str = builder_str.reverse().toString();
    return reversed_str;
    
    in one line => return new StringBuilder(str).reverse().toString()
    
    ***************************************************
    
    // Manipulate with replaceAll() method to string and Passed or removed whatever chars    
    
    input => "fun123&!!    time"
    String sen_replaced = sen.replaceAll("[^a-zA-Z0-9 ]", ""); => output: "fun123    time"
    
    String[] words = sen_replaced.split(" "); // {"fun123","time"}
    
    ***************************************************