String Class Notes

package strings;

public class StringMethods {

    public static void main(String[] args) {
        // strings are immutable meaning you cannot change the contents after creating
        //    what do we mean by this
        //    show THE HEEP and how immutable objects are stored there until flushed (or never)
        //      The main difference between heap and stack is that stack memory is used to store local variables and function call while
        //      heap memory is used to store objects in Java.
        // strings can be one letter but use CHAR for this
        // class string is already provided by Jave so you don't need to make this yourself

        // show them how Ctrl Click on string will show the class designation code ON SOME COMPLIERS
        // NOT ours!

        // since Java 9 string is an array of Bytes (before it was an array of Char)
        // less space Char 8 bytes

        String s = "  Elementary Elements   ";

        String s2 = s.toLowerCase();  //  elementary elements
        System.out.println("s2 ="+s2);

        // show them userinput. to show command options
        // just typing this String s9 = s. will give them the options
        // shows all this INSTANCE METHODS

        s = s.toUpperCase();
        System.out.println("s="+s);

        s2 = s2.trim();                     // gets rid of the blanks before and after
        System.out.println("s2="+s2);

        int len = s2.length();              // lenght of the string
        System.out.println("len = "+len);

// show them command first, change indesy for them
//        THENask them to build a for loop around it as inclass work
// give them five minutes and then show them
        char indexy = s2.charAt(4);
        System.out.println(" char at 4 " + " = "+ indexy);  // note indexes start at 0 for arrays

        for (int i=0; i < len ;  i++)       // walk through each indexy of the string
        {
            char c = s2.charAt(i);
            System.out.println(" char at "+ i + " ="+ c);
        }

        int count =0;
        for (int i=0; i < len ;  i++)       // Finds "e"
        {
            char c = s2.charAt(i);
            if (c == 'e')
                count += 1;
        }

        System.out.println("found " + count + " e's");

        String s3 = s2.substring(6);        // substring at 6 shows the 6 to the end of string
        String s4 = s2.substring(6,10);     // using range to just print out what we want

        System.out.println("s2.substring(6)="+ s3);
        System.out.println("s2.substring(6,10)="+ s4);

        int index = s2.indexOf('e');        // indexOf finds the first e's index number
        System.out.println("index ="+index);

        index = s2.indexOf('e' , index +1); // repeating it finds the next e's index number
        System.out.println("index ="+index);


        index = s2.indexOf('e' , index +1); // and the next the next e's index number
        System.out.println("index ="+index);


        index = s2.indexOf('e' , index +1); // and the next the next e's index number
        System.out.println("index ="+index);


        int start =0;
        int index2;
        int count2 =0;

        System.out.println("What is this?");    // this finds letters in string and tells you what index
        do
        {
            index2 = s2.indexOf('e', start);
            if ( index2 >= 0)
            {
                start = index2 +1;
                System.out.println("Found an e at " + index2);
                count2 += 1;
            }

        } while (index2 >= 0);

        System.out.println("Found " + count2 +" e's");

        start = 0;
        count2 = 0;
        do
        {
            index2 = s2.indexOf("men", start);
            if ( index2 >= 0)
            {
                start = index2 +1;
                System.out.println("Found men  at " + index2);
                count2 += 1;
            }

        } while (index2 >= 0);

        System.out.println("Found " + count2 +" men's");
    }
}