Architecture

Data types

Control statement

Flowchart

while loop

public class WhileLoopDemo {
        public static void main(String[] args) {
            int i = 1;
            while (i < 6) {
                System.out.println("Hello World");
                i++;
            }
        }
    }

Output

Hello 1
Hello 2
Hello 3
Hello 4
Hello 5

for loop

    public class ForLoopDemo {
        public static void main(String[] args) {

            for (int i = 1; i <= 5; i++) {
                System.out.println("Hello " + i);
            }
        }
    }

output

Hello 1
Hello 2
Hello 3
Hello 4
Hello 5

if else

    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

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

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:

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

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

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)

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

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.

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.