# Java part -1 ## Architecture ![Java virtual machine](http://www.cseworldonline.com/javatutorial/javaimages/java-virtual-machine.png align="left") ## Data types ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711426129307/13c94331-2425-44e7-b4cc-7e2c93063650.jpeg align="left") ## Control statement ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711427151411/08b4b19e-ad2f-4460-b1d6-9c99cd953ebe.png align="left") ### Flowchart ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711432345658/5c60f5da-d496-42fd-a22d-d354a079ca77.png align="left") ### while loop ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711434124549/e6e61858-afdb-40a2-acef-17accf83f3d7.png align="center") ```java public class WhileLoopDemo { public static void main(String[] args) { int i = 1; while (i < 6) { System.out.println("Hello World"); i++; } } } ``` Output ```plaintext Hello 1 Hello 2 Hello 3 Hello 4 Hello 5 ``` ### for loop ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711434388681/c41867fe-2d1d-456e-bd93-f1f6f1c085c1.png align="left") ```java public class ForLoopDemo { public static void main(String[] args) { for (int i = 1; i <= 5; i++) { System.out.println("Hello " + i); } } } ``` output ```plaintext Hello 1 Hello 2 Hello 3 Hello 4 Hello 5 ``` ### if else ```java public class IfelseLoopDemo { public static void main(String[] args) { int value = 5; if (value == 5) { System.out.println("value is eq = 5"); } else { System.out.println("value is not eq = 5"); } } } ``` output ```plaintext value is eq = 5 ``` ### Break * The `break` statement is used to **terminate a loop early**. When encountered inside a loop, it immediately exits the loop, skipping any remaining iterations. * Example: Printing numbers from 0 to 9, but stopping when the value is 5 ```java public class BreakExample { public static void main(String[] args) { for (int i = 0; i < 10; i++) { if (i == 5) break; System.out.println("i: " + i); } System.out.println("Out of Loop"); } } ``` output: ```plaintext i: 0 i: 1 i: 2 i: 3 i: 4 Out of Loop ``` ### continue * The `continue` statement is used to **skip the current iteration** of a loop and proceed to the next iteration. * Example: Printing numbers from 0 to 9, but skipping the value 4 ```java public class ContinueExample { public static void main(String[] args) { for (int i = 0; i < 10; i++) { if (i == 4) continue; System.out.println(i); } } } ``` output ```plaintext 0 1 2 3 5 6 7 8 9 ``` ### Debugging in java * it's very important to solve/find the error in your code. How to Debug 1. set `Breakpoints` 2. Debug as 3. step over (F6) ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711439865496/19a71c1b-c642-420f-ab05-2c996105e108.png align="center") note: before i have used `println` so that i didn't get expected output. after debugging i find this. and changed to `print` > step over: executes the current line of code without entering method calls. > > step into: enters the method call and executes its code line by line. ### Arrays ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1711440866974/e0bc43ea-bebd-4001-87e1-801319238685.png align="center") ```java int[] arr={10,20,30,40}; // access the element System.out.println("Element at 4th place"+arr[3]); ``` ### Methods * A **method** is a block of code which only runs when it is called. * You can pass data, known as parameters, into a method. ```java public class MethodDemo { public static void main(String[] args) { // method call int res = sumOfTwoNum(10, 5); System.out.println(res); } // method creation public static int sumOfTwoNum(int a, int b) { return a + b; } } ``` `static` - means that the method belongs to the Main class (no need to create object for this) not a problem if you not understand this keyword, you will understand this in next part of this java series.