> For the complete documentation index, see [llms.txt](https://nissan-goldberg.gitbook.io/java101/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nissan-goldberg.gitbook.io/java101/lesson-2/untitled.md). # Lesson 2 - While Todays lesson * More Conditionals - `if` and `else` * `while` , `break` and `do-while` ## שאלת חימום מצא את המקסימום בין 4 מספרים ```java public class Main { public static void main(String[] args) { int a = 1, b=71, c=3, d= 10, max; max = (a >b) ? a : b; max = Math.max(max, c); //same thing max = (max >d) ? max : d; System.out.println(max); } } ``` ``` 71 ``` ## כמה ספרות וכמה אפסים קלוט מספר n * הדפס מספר הספרות * הדפס מספר האפסים ```java public class Main { public static void main(String[] args) { int num = MyConsole.readInt("enter a number: "); System.out.println("You entered a " + (num >= 0 ? "positive" : "negative") +" number"); int countZeros=0; int countDigits=0; int absNum = num>=0 ? num : -num; if (num==0){ countZeros=1; countDigits=1; } while (absNum > 0) { if (absNum%10==0) countZeros++; absNum /= 10; countDigits++; } System.out.println("number of digits: " + countDigits); System.out.println("number of zeros: " + countZeros); } } ``` ``` enter a number: -30012 You entered a negative number number of digits: 5 number of zeros: 2 ``` זה if מקוצר ```java int absNum = num>=0 ? num : -num; ``` ![](https://i.ibb.co/GJTgFyL/ternary-conditional-operator.png) ### version 2 let `num` be a random number from `-1000` until `9999` (including) ```java int max = 10_000, min = -1_000; int num = (int) ((Math.random() * (max - min)) + min); //random number from -1,000 to 9,999 (including) System.out.println("Random num:" + num); ``` ``` Random num:6318 You entered a positive number number of digits: 4 number of zeros: 0 ``` > Note: it includes the min but not the max \[min, max) ## Rotate Square ![](https://i.ibb.co/gt5vQbR/cube-shifter-easy.png) יש לסובב את הקוביה ```java public class Main { public static void main(String[] args) { int a = 1, b =2, c=3, d=4, temp; temp = d; d = c; c = b; b = a; a = temp; System.out.println("a: " + a + "\nb: " + b + "\nc: " + c + "\nd: " + d); } } ``` ``` a: 4 b: 1 c: 2 d: 3 ``` #### טבלת מעקב ![track-table](https://i.ibb.co/bzs5kZK/track-table.png) ### Version 2 : n right or left shifts ![](https://i.ibb.co/t4v0v6M/cube-shifter.png) קלוט מספר n: * אם הוא חיובי אז סובב n פעמים ימינה * אם הוא שלילי אז סובב n פעמים שמאלה ```java public class Main { public static void main(String[] args) { int a = 1, b =2, c=3, d=4, temp; boolean isRightShift=true; int n_shifts = MyConsole.readInt("enter:\n* posivite num for right shift" + "\n* negative for left shift\ninput :"); if (n_shifts<0) { isRightShift = false; n_shifts = n_shifts * -1; //since while works on positive number, otherwise we would need 2 different whiles System.out.println("Left shifting " + n_shifts +" times"); } else if (n_shifts==0) System.out.println("No shifts"); else System.out.println("Right shifting " + n_shifts +" times"); while (n_shifts>0){ if (isRightShift) { temp = d; d = c; c = b; b = a; a = temp; n_shifts = n_shifts-1; System.out.println("a: " + a + "\tb: " + b + "\tc: " + c + "\td: " + d); }else { temp = a; a = b; b = c; c = d; d = temp; n_shifts = n_shifts-1; System.out.println("a: " + a + "\tb: " + b + "\tc: " + c + "\td: " + d); } } } } ``` ``` enter: * posivite num for right shift * negative for left shift input : -2 Left shifting 2 times a: 2 b: 3 c: 4 d: 1 a: 3 b: 4 c: 1 d: 2 ``` #### note since `while (n_shifts>0)` checks for positive numbers and we do `n_shifts = n_shifts-1;` inside the while loop without `n_shifts = n_shifts * -1` if we have a left shift we would need **another** ***while*** loop ## Find Aprox. log2 מצא עבור קלט x את: $$ log\_2x=answer $$ קודם כל בא נבין מה קורה כאן $$ 2^3=2*2*2=8 $$ $$ log\_28=3 $$ אם הוא לא חזקה שלמה הדפס את חזקה שלמה ועוד .x ```java public class Main { public static void main(String[] args) { float x = (float)MyConsole.readDouble("enter positive num: "); while (x<0.) x = (float)MyConsole.readDouble("Try again\nPlease enter a positive num: "); // float x = 1<<10; // float x = 1_024f; float original = x; int count = 0; boolean isPowOf2 = false; while(x > 2) { x = x / 2; count +=1; if (x==2.){ System.out.println("log_2("+original+")="+(count+1)); isPowOf2 = true; } } if (isPowOf2==false) System.out.println("log_2("+original+")="+count + ".x"); } } ``` ``` enter num: 1024 log_2(1024.0)=10 ``` 2nd run ``` enter num: 1025 log_2(1025.0)=10.x ``` > To find the real answer we should use a Talyor series. ## Find Parallel lines מצא האם 2 ישרים: * מקבילים * מאונכים * או לזה זה ולא זה ![](https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3A3ceeb0ba9414cc883c09344f3559186ae97bd2434e1d67cdfe4483d5%2BIMAGE_TINY%2BIMAGE_TINY.1) [img source](https://www.ck12.org/c/geometry/parallel-lines-in-the-coordinate-plane/lesson/Parallel-Lines-in-the-Coordinate-Plane-BSC-GEOM/) ![Find The Slope Of A Line That Passess Through 2 Points - YouTube](https://i.ytimg.com/vi/KC3Eh8ZH3F0/maxresdefault.jpg) [img source](https://www.google.com/url?sa=i\&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DKC3Eh8ZH3F0\&psig=AOvVaw3g34ALI2noOZ2DNL3ck-29\&ust=1615891581323000\&source=images\&cd=vfe\&ved=0CA0QjhxqFwoTCMDGurCPsu8CFQAAAAAdAAAAABAc) ![](https://i.ibb.co/SVgzZVN/slopes.png) ```java public class Main { public static void main(String[] args) { //parallel - 2 greens // int l1_x1 = 0, l1_y1 = 0, l1_x2 =3, l1_y2=2; // int l2_x1 = 3, l2_y1 = 0, l2_x2 =0, l2_y2=-2; //perpendicular - green and orange // int l1_x1 = 0, l1_y1 = 0, l1_x2 =3, l1_y2=2; // int l2_x1 = 0, l2_y1 = 0, l2_x2 =-2, l2_y2=3; //neither - green and purple int l1_x1 = 0, l1_y1 = 0, l1_x2 =3, l1_y2=2; int l2_x1 = 0, l2_y1 = 0, l2_x2 =1, l2_y2=3; double Δ_l1_y = l1_y1-l1_y2, Δ_l1_x = l1_x1-l1_x2; double Δ_l2_y = l2_y1-l2_y2, Δ_l2_x = l2_x1-l2_x2; double slope_l1 = Δ_l1_y/Δ_l1_x; double slope_l2 = Δ_l2_y/Δ_l2_x; if (slope_l1==slope_l2) System.out.println("The lines are parallel\n" + "slope is:" + slope_l1); else if((-1*Δ_l1_x)/Δ_l1_y==slope_l2) System.out.println("The lines are perpendicular\n" + "* slope of line 1 :" + slope_l1 + "\n* slope of line 2 :" + slope_l2); else System.out.println("lines are neither:" + "\n* parallel\n* perpendicular" + "\n\t* slope of line 1 :" + slope_l1 + "\n\t* slope of line 2 :" + slope_l2); } } ``` ``` lines are neither: * parallel * perpendicular * slope of line 1 :0.6666666666666666 * slope of line 2 :3.0 ``` --- # Agent Instructions This documentation is published with GitBook. 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