Lesson_4: Control flow

1. if(), if() else(), if() else if() else()

a) Simple if else case

Scanner in = new Scanner(System.in);
int a = in.nextInt();
if (a > 0) {
    System.out.println("Positive");
} else if (a == 0) {
    System.out.println("Neutral");
} else {
    System.out.println("Negative");
}

System.out.println("Continue...");

b) Wrong if else case

Scanner in = new Scanner(System.in);
int grade = in.nextInt();
if(grade > 90 && grade <= 100) {
    System.out.println("A");
} else if (grade > 80) {
    System.out.println("B");
} else {
    System.out.println("Fail");
}

System.out.println("Continue...");

When we input for example 150 code crashes.


Random random = new Random();
int grade = random.nextInt(100);
if (grade > 90) {
    System.out.println(grade + " A");
} else if (grade > 80) {
    System.out.println(grade + " B");
} else if (grade > 70) {
    System.out.println(grade + " C");
} else if (grade > 60) {
    System.out.println(grade + " D");
} else if (grade > 50) {
    System.out.println(grade + " F");
} else {
    System.out.println(grade + " Failed");

} 


Statement problem:

int i = 2;
if (i < 3) {
    int ii = 10;
}
System.out.println(ii);
int i = 2;
if (i < 3) 
    int ii = 10;


2. While statement:

double d = Math.random();
System.out.println(d);

while (d < 0.5) {
    d = Math.random();
    System.out.println("inside while: " + d);
}

System.out.println("Outside while: " + d);


In while we can not use this particular case:

int[] arr = {1, 2, 3, 4, 5, 6};
int i = 3;
int k = 0;
while (i < arr[k]) {
    System.out.println(arr[k++]);
}


3. For dovru:

For dovru ile Fibonacci ardicilliginin cap edilmesi:

// 0, 1, 1, 2, 3, 5, 8, 13, 21
int first = 0;
int second = 1;
int result = 0;
for(int i = 0; i < 10; i++) {
    System.out.println(first);
    result = first + second;
    first = second;
    second = result;
}


for(char c = 0; c < 255; c++) {
    System.out.println("value : " + (int)c + " character : " + c);
}


Mesele1: 

*****

*****

*****

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        System.out.print(" * ");
    }
    System.out.println();
}


Mesele2:

*

**

***

for (int i = 1; i <= 10; i++) {
    for (int j = 0; j < i; j++) {
        System.out.print(" * ");
    }
    System.out.println();
}


Mesele3:

      *

    **

  ***

****

for (int i = 1; i <= 10; i++) {
    for (int j = 10; j > 0; j--) {
        if(j > i)
        System.out.print(" ");
        else
            System.out.print("*");
    }
    System.out.println();
}


Mesele4:

****

***

**

*

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        if(j < i)
        System.out.print(" ");
        else
            System.out.print("*");
    }
    System.out.println();
}


Mesele5:

******

*        *

******

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        if(i == 0 || i == 9 || j == 0 || j == 9) {
            System.out.print("*");
        } else
            System.out.print(" ");
    }
    System.out.println();
}


Mesele6:

********

*  *        *

*     *     *

*       *   *

*          **

********

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        if(i == 0 || i == 9 || j == 0 || j == 9 || i == j) {
            System.out.print("*");
        } else
            System.out.print(" ");
    }
    System.out.println();
}


Mesele7:

********

*  *      * *

*     *     *

*   *   *   *

* *        **

********

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        if(i == 0 || i == 9 || j == 0 || j == 9 || i == j || i + j == 9) {
            System.out.print("*");
        } else
            System.out.print(" ");
    }
    System.out.println();
}


Mesele8:

********

             *

*******

* 

*******

            *

*******

int flag = 1;
for (int i = 0; i < 10; i++) {
    if(i % 2 == 0) flag++;
    for (int j = 0; j < 10; j++) {
        if(i % 2 == 0) {
            System.out.print("*");
        } else {
            if(j == 9 && flag % 2 == 0) {
                System.out.print("*");
            }
            if(j == 0 && flag % 2 == 1) {
                System.out.print("*");
            }
            System.out.print(" ");
        }
    }
    System.out.println();
}


Break:

for(int i = 1; i <= 5; i++) {
    if(i == 4) break;
    System.out.println(i + " " + i * i);
}


Continue:

for(int i = 1; i <= 5; i++) {
    if(i == 4) continue;
    System.out.println(i + " " + i * i);
}


Label:

outer:
for (int i = 0; i < 10; i++) {
    inner:
    for (int j = 0; j < 10; j++) {
        if(j == 5) break inner;
        System.out.println(i + " : " + j);
    }
    System.out.println("-------------------------------");
}


Label: hour example

for (int hours = 0; hours < 24; hours++) {
    System.out.println("Start of outer loop");
    for (int minutes = 0; minutes < 60; minutes++) {
        System.out.println(hours + " : " + minutes);
        if (minutes == 30) break;
    }
    System.out.println("End of outer loop");
}


indi ise men isteyirem ki, minutes 30 olduqda outer loop dayansin:

for (int hours = 0; hours < 24; hours++) {
    System.out.println("Start of outer loop");
    for (int minutes = 0; minutes < 60; minutes++) {
        System.out.println(hours + " : " + minutes);
        if (minutes == 30) {
            hours = 24;
            break;
        }
    }
    System.out.println("End of outer loop");
}




Switch case:

final ve blank final iwledilmesi:

int month = new Scanner(System.in).nextInt();
final int i;
i = 5;
switch (month) {
    case i: 
}

A switch case works with the byte, short, char, int primitive data types. Also it works with Enumerated, String, Byte, Short, Character and Integer reference types. 


Return in switch case:

public static Integer square(int n) {
    switch (n) {
        case 1:
            return 1;
        case 2:
            return 4;
        default:
            return null;
    }
}


Arrays. One dimentional array.

int[] array1 = new int[10];
Integer array2[] = new Integer[10];
int[] array3 = {1, 2, 3, 4};


Primitive tiplerde default value her bir primitive mexsus default value olur, referanslarda ise null olur.

int[] array1 = new int[10];
Integer array2[] = new Integer[10];

for(int i = 0; i < array1.length; i++) {
    System.out.println(array1[i]);
    System.out.println(array2[i]);
}


For each:

int[] arr = {1, 2, 3, 4, 5};

for (int i: arr) {
    System.out.println(i);
}


For each loop icinde eger biz deyer deyiwmek istesek o zaman bu mumkun olmayacaq.

int[] arr = {1, 2, 3, 4, 5};
for (int i: arr) {
    i = 10;
}

for (int i: arr) {
    System.out.println(i);
}


2D arrays:

int[][] arr1 = new int[3][];
int[][] arr2 = {{1, 2}, {3, 4}, {5, 6}};
for(int i = 0; i < arr2.length; i++) {
    for(int j = 0; j < arr2[i].length; j++) {
        System.out.println(arr2[i][j]);
    }
}

int[] a1 = {1, 2, 3};
int[] a2 = {4, 5, 6, 7};
int[] a3 = {8, 9};
int[][] arr = {a1, a2, a3};

int[][] b = new int[2][];
b[0] = new int[3];
b[1] = new int[5];


Alqoritmik sual 3:

Ferz edek ki 1000000 ehalimiz var ve onlarin yashi 0-100 arasindadir. Buna esasen statistika cixarilmalidir ve her yasha uygun nece nefer oldugu bilinmelidir.

int[] people = new int[10];
Random random = new Random();
for(int i = 0; i < people.length; i++) {
    int rand = random.nextInt(10);
    System.out.println(rand);
    people[i] = rand;
}

int[] result = new int[10];

for(int i = 0; i < people.length; i++) {
    int age = people[i];
    result[age] = ++result[age];
}

for(int i = 0; i < result.length; i++) {
    System.out.println(i + " : " + result[i]);
}





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