Hello guys I need an explanation for the study guide to help

Hello guys, I need an explanation for the study guide to help me to understand :

Study Guide

Know:

1. Two ways to instantiate an array:

int[] myInts = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};

and

int[] myInts = new int[100];

2. Two ways to traverse an array:

for (int i = 0; i < myInts.length; i++)

{

myInts[i] = i + 1;

}

and

for (int myValue : myInts)

{

System.out.println(myValue);

}

3. Be able to trace through some looping structures and determine what the output/effect would be:

int x = 2;

int y = 5;

while (x >= 5)

{

   System.out.print(x * y + \" \");

          x--;

}

4. Nested loop:

for    (x = 1; x <= 5; x++)

{

      for ( y = 0; y <= x; y++ )

{

     System.out.print(x * y + \" \");

}

    System.out.println();

}

5. Conditionals:

public static void main(String[] args)

{

int x;

int y;

Scanner kb = new Scanner(System.in);

System.out.println(\"Enter two integers for x and y: \");

x = kb.nextInt();

y = kb.nextInt();

if (x > 0 && y > 0)

{

    System.out.print(\"You are\");

if (x > 10)

System.out.print(\" way cool\");   // <-No braces required if only one statement...

else //

if (y < 10)

System.out.print(\" crazy\");

else //

System.out.print(\" man\");

}

else //

{

if (x < 0)

{

System.out.print(\"We are\");

}

else //

{ if (y < 0)

System.out.print(\"They are\");

else //

System.out.print(\" the best\");

}

System.out.print(\" OK\");

}

System.out.println(\", if you know what I mean.\");

}

x:                                   y:                                    You are crazy, if you know what I mean.

x:                                    y:                                    We are OK, if you know what I mean.

x:                                    y:                                    We are the best OK, if you know what I mean.

x:                                    y:                                    You are the best OK, if you know what I mean.

x:                                    y:                                   the best OK, if you know what I mean.

x:                                  y:                                  OK, if you know what I mean.

x:                                  y:                                    You are way cool, if you know what I mean.

x:                                  y:                                    They are the best OK, if you know what I mean

x:                                  y:                                    They are OK, if you know what I mean

and

‘Complete the following:’

Scanner kb = new Scanner(System.in);

int choice = 0;

do{

     System.out.println(\"\ Please choose \");

    System.out.println(\"1. Do this\");

     System.out.println(\"2. Do that\");

    System.out.println(\"3. Do the other thing\");

     System.out.println(\"4. Quit\");

    System.out.print(\"Enter option--> \");

     choice = kb.nextInt();

     kb.nextLine();

     switch (_________)

{

___________:

     System.out.print(\"You selected option 1\");

____________;

___________:

     System.out.print(\"You selected option 2\");

____________;

___________:

System.out.print(\"You selected option 3\");

____________;

___________:

              System.exit(0);

      }

}while (true);

6. String class. Be able to substring, isolate individual characters and to compare two Strings.

String myString = “Hello”;

System.out.println(myString.charAt(1));

System.out.println(myString.substring(1, 3));

System.out.println(myString.substring(1));

If (myString.equals(yourString))

Thank you...

Solution

1. Two ways to instantiate an array:

int[] myInts = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};

// myInts is an array of 10 integers whose values are initialized---declaration and initialization

int[] myInts = new int[100];

// myInts is an array of 100 integers --- declaration only not initialization

2. Two ways to traverse an array:

for (int i = 0; i < myInts.length; i++)

{

myInts[i] = i + 1;

}

// myInts[0] = 1, myInts[1] = 2, myInts[2] = 3......................

for (int myValue : myInts)

{

System.out.println(myValue); //display the values of myInts

}

3. Be able to trace through some looping structures and determine what the output/effect would be:

int x = 2;

int y = 5;

while (x >= 5)

{

   System.out.print(x * y + \" \");

          x--;

}

Output:

No Output as While condition is false (x = 2 <5) so while wil never execute and nothing will be displayed .

4. Nested loop:

for    (x = 1; x <= 5; x++) // 5 rows

{

      for ( y = 0; y <= x; y++ ) // for each row it will display x columns starting from 0 to x with each value = x*y

{

     System.out.print(x * y + \" \");

}

    System.out.println();

}

output:

5. Conditionals:

public static void main(String[] args)

{

int x;

int y;

Scanner kb = new Scanner(System.in);

System.out.println(\"Enter two integers for x and y: \");

x = kb.nextInt();

y = kb.nextInt();

if (x > 0 && y > 0)

{

    System.out.print(\"You are\");

if (x > 10)

System.out.print(\" way cool\");   // <-No braces required if only one statement...

else //

if (y < 10)

System.out.print(\" crazy\");

else //

System.out.print(\" man\");

}

else //

{

if (x < 0)

{

System.out.print(\"We are\");

}

else //

{ if (y < 0)

System.out.print(\"They are\");

else //

System.out.print(\" the best\");

}

System.out.print(\" OK\");

}

System.out.println(\", if you know what I mean.\");

}

x: >0                                  y: >0,y<10                              You are crazy, if you know what I mean.

x: <0 ,                                 y: >0                                 We are OK, if you know what I mean.

x:   <0                               y: >0                                We are the best OK, if you know what I mean.

x:   >0                               y:   >0                               You are the best OK, if you know what I mean.

x: <0                                 y: >0                                   the best OK, if you know what I mean.

x: <0                                 y: <0                                  OK, if you know what I mean.

x: >10                                 y: >0                                 You are way cool, if you know what I mean.

x:   >0                                y: >0                                 They are the best OK, if you know what I mean

x: >0                                 y: <0                                 They are OK, if you know what I mean

and

‘Complete the following:’

Scanner kb = new Scanner(System.in);

int choice = 0;

do{

     System.out.println(\"\ Please choose \");

    System.out.println(\"1. Do this\");

     System.out.println(\"2. Do that\");

    System.out.println(\"3. Do the other thing\");

     System.out.println(\"4. Quit\");

    System.out.print(\"Enter option--> \");

     choice = kb.nextInt();

     kb.nextLine();

     switch (choice)

{

case 1:

     System.out.print(\"You selected option 1\");

     break;

     case 2:

     System.out.print(\"You selected option 2\");

     break;

     case 3:

System.out.print(\"You selected option 3\");

break;

case 4:

              System.exit(0);

      }

}while (true);

6. String class. Be able to substring, isolate individual characters and to compare two Strings.

import java.util.*;

class myString
{
   public static void main (String[] args)
   {
       Scanner scan = new Scanner(System.in);
       String myString = \"Hello\";

for(int i=0;i< myString.length();i++)
System.out.println(myString.charAt(i));

//System.out.println(myString.substring(1, 3));

//System.out.println(myString.substring(1));

System.out.println(\"Enter your String\");
String yourString = scan.next();
if (myString.equals(yourString))
System.out.println(\"Strings are equal\");
else
System.out.println(\"Strings are not equal\");

   }
}

output: