All in Java programming QUESTION 1. Why does this code not work? Provide a working version? ---------------- ```typescript /** * Code for Question 1. * * Remove values less than 10 from an array * * @param list */ export function question1_removeSmallNumbers(list: (number | undefined)[]) { for (let i = 0; i < list.length; i++) { const n = list[i] if (n && n < 10) { console.log('removing', n) list.splice(i, 1) } } } ``` QUESTION 2: Programming Task ---------------- Classes that implements the following interfaces, assuming that all methods are used with approximately the same frequency. Explain why you chose the data structures you used. ```typescript export interface Item { id: string tag: string } export interface ItemStore { /** * Adds an {@link Item} to the store, replacing any existing item with the * same {@link Item#id} value. */ put: (item: Item) => void /** * Retrieves the {@link Item} with the given {@link Item#id} value, or * null if no such {@link Item} exists in the store. */ get: (id: string) => Item | null /** * Delete all {@link Item}s with the specified tag. */ dropAllByTag: (tag: string) => void /** * Returns the number of Items in the store */ size: () => number } ``` QUESTION 3: Asynchronous Event Debugging ---------------- The following line of code works most of the time: ```js ReactDOM.render(, document.getElementById('app-container')); ``` But, occasionally during browser startup it fails with an exception because `document.getElementById('app-container')` returns `null`. The following changes address the issue and work reliably. Explain if this code works, but the original code would sometimes fail. ```js window.addEventListener('load', () => { ReactDOM.render(, document.getElementById('app-container')); }) ``` You may use https://developer.mozilla.org/en-US/docs/Web/API/Window/load_event for reference about the `Window: load event`. QUESTION 4: Debugging ---------------- ``` class Bug1 { _rating: number | null = null rating() { return this.rating; } } export function question4() { const bug = new Bug1() return `Rating is ${bug.rating()}` } ``` The function `question4` above does not return the expected string: 'Rating is null'. Instead the string below is returned. ``` Ratingisrating(){ returnthis.rating; } ``` Debug the class `Bug1` and correct it so that it returns the expected string `Rating is null`. QUESTION 5: Spread Operator ---------------- Given the function below: ``` export function question5() { let orig = { prop1: 'p1', prop2: 'p2', } let modified = orig orig.prop1 = 'm1' if (orig === modified) { console.log('orig and modified are the same') } if (modified.prop1 === 'm1') { console.log('orig.prop1 is m1') } modified = { ...orig, prop2: 'm2' } if (orig === modified) { console.log('orig and modified are still the same') } if (modified.prop1 === 'm1') { console.log('orig.prop1 is m1') } if (modified.prop2 === 'm2') { console.log('orig.prop1 is m2') } } ``` What is the output? There are two nearly identical blocks of code: ```ts if (orig === modified) { console.log('orig and modified are the same') } ``` and ```ts if (orig === modified) { console.log('orig and modified are still the same') } ``` If one or either of the `console.log` lines was skipped, explain why. BONUS: Programming Puzzle Bonus! ---------------- A string of ASCII text has been encrypted using the following algorithm: * Use the bytes "MOEBIUS" as the key. * Working one byte at a time, xor the next byte of data with the next byte in the key. * When the end of the key is reached, wrap around to the first byte again. * Base-64 encode the data. For example, the text "Simple is better than complex." encrypts to "HiYoMiUwcyQ8ZSAsIScoPWU2ITQ9bSwqLzk5NjVh". The key is repeated as follows while XOR-ing bytes: ``` Simple is better than complex. MOEBIUSMOEBIUSMOEBIUSMOEBIUSMO ``` A program to reverse this process and decrypt the following message. Use any programming language you like. Provide both your program and the decrypted message. ``` DiArJTs0JzgjJDYgOj0+Y2U7JiBzPiApNCwxczknIGIrOj04PGUzPDAgOSYqLGhfWW1vZW JpdXNtb2ViaXVzbW9lYml1c21vZWJpdXNtb2ViaXVzY2hibEN1c21vZWJpe3RqYWViaXVz bWFlYml1c21vZWhucnltb2VicwoPYhB/Yml1c21hT2JpdXNtb38dFXoMd29lYhYJe2IQZW Jnb31nEBltFn9zbW9/YmYJc3dvZWxue2ljaGtIaXV9amhreGl6D211ZWJpe3xkE2ViaXJp amVlbRV1eW11ZWJue31qYWViZGhpInV4b0N1aRITah1zcn13dX9saXVzbWhlaG5yeW1vZW JjdXRjaGpsbnUMEWdqHW57dHdoa2VDdWltYBlic3Vpd3V/eGl1c21vbx0Vegxnb2ViaXV+ cG8qYnR4c21gbB5pdXNtaE9iaXJ9Y2hlYm5vaXdoZWJpdXNnb2oeaX9zbW9lYmdyfGNoa2 JpdXRHb2ViaXVzbW9lYml1c21vZWJpdXljYW9iaXVzbW9lYmlvWQ== ``` > NOTE: This block uses the "MIME" flavor of Base64 encoding. > Depending upon your Base64 decoder, you may need to remove the "=" padding