Java 13_String & BiuldString

Create a String

        String randomString = "I'm just a random string";

Use quotes in a string escape it with \

        String gotToQuote ="He said, \"I'm here\"";

Other common Escape Codes
* \n : Newline
* \b : Backspace
* ' : Apostrophe
* " : Quote
* \ : Backslash

Combine Strings with a +

        System.out.println(randomString + " " + gotToQuote);

Add other data type to the string with a +

        int numTwo = 2;
        System.out.println(randomString + " " + numTwo);

Convert primitive types to a string with toString

         * String byteString = Byte.toString(bigByte);
         * String shortString = Short.toString(bigByte);
         * String intString = Integer.toString(bigInt);
         * String longString = Long.toString(bigByte);
         * String floatString = Float.toString(bigByte);
         * String doubleString = Double.toString(bigByte);
         * String booleanString = Boolean.toString(bigByte);

Convert from String to primitives with parse

         * int stringToInt = Integer.parseInt(intString);
         * parseSort, parseLong, parseByte, parseDouble, 
         * parseBoolean, parseFloat
         */

Compare strings with equals or equalsIgnoreCase

            String uppercaseStr = "BIG";
        String lowercaseStr = "big";    
        if(uppercaseStr.equals(lowercaseStr))
        {
            System.out.println("They're equal");
        }
        
        if(uppercaseStr.equalsIgnoreCase(lowercaseStr))
        {
            System.out.println("Same letters");
        }
        
        

CharAt returns the character in a string

        System.out.println("2nd Character: " + letters.charAt(1));
        

CompareTo

                String letters = "abcde";
        String moreLetters = "fghijk";
                //compareto returns 0 if strings are equal
        // Returns a negative number if letters comes before moreLetters
        // Returns a positive number if letters comes after moreLetters
        // There is also a compareToIgnoreCase()
        System.out.println(letters.compareTo(moreLetters));

Contains()

          //Contains()returns a boolean depending on whether the 
        // String contains the String you pass it
        System.out.println(letters.contains("abc"));
        
        // endsWith() checks if the String ends with the String you pass
        System.out.println(letters.endsWith("de"));
        
        // startsWith() works similar to endsWith()

IndexOf()

         //returns the 1st index that matches the String passed
        System.out.println(letters.indexOf("cd"));
        
        // You can also specify the index to start searching from
        // indexOf(StringToLookFor, IndexStartPosition)
        
        // lastIndexOf() works like indexOf except it starts from the 
        // end of the String you are searching

length()

         //returns the number of characters in a String
        System.out.println("Length of string: " + letters.length());

Replace()

              //replaces every occurrence of the first String with
        // the second String you provide
        System.out.println(letters.replace("abc", "xy"));

split()

        // You can create an array of Strings with split()
        // You define how to break up the String using a delimiter
        // If you had 123,456 and used the delimiter "," you would
        // create the array [123,456]
        String[] letterArray = letters.split("");

toString() converts the array into a String to print it

        System.out.println(Arrays.toString(letterArray));

toCharArray()

        //toCharArray() inserts every character in the string into
        // separate indexes in an array 
        char[] charArray = letters.toCharArray();
        
        System.out.println(Arrays.toString(charArray));

substring()

        // substring() returns a String starting at the first index
        // through the last index provided
        System.out.println(letters.substring(1,4));

toUpperCase() & toLowerCase()

        // toUpperCase() converts all letters into uppercase
        // toLowerCase() does the opposite
        System.out.println(letters.toUpperCase());

trim()

        // trim() gets rid of leading and trailing white space
        System.out.println(randString.trim());

StringBiuld

A String is immutable, which means every time you change a String a new version is created in memory.If you manipulate Strings allot use a StringBuilder

Create a StringBuilder

        // It has a fixed space in memory
        StringBuilder randSB = new StringBuilder("A random string");

adds

        // append() adds anything to the end of a SB
        System.out.println(randSB.append(" again"));

    // append() permanently effected the StringBuilder
        System.out.println(randSB);

delete()

        // delete() removes part of the SB from first index to the last
        System.out.println(randSB.delete(15, 21));
        
        // deleteCharAt(index) is used to delete individual chars

capacity()

    // capacity() returns the number of indexs for the SB
        System.out.println(randSB.capacity());

ensureCapacity()

                //ensureCapacity() increases the capacity for the SB
        randSB.ensureCapacity(60);
        System.out.println(randSB.capacity());

length()

        // length() returns the number of characters in the SB
        System.out.println(randSB.length());

trimToSize()

        // trimToSize() forces capacity to equal length
        randSB.trimToSize();

insert()

    // insert() inserts at the index you provide anything
        System.out.println(randSB.insert(1, "nother"));

toString

    // toString converts a SB into a String
        String oldSB = randSB.toString();
    
        /* StringBuilders also have the same methods as Strings
         * charAt(), indexOf(), lastIndexOf(), subString()
         */