public static void main(String[] args) {
Scanner userInput = new Scanner(System.in);
int x = 20;
String choice = "";
while(x!=0) {
System.out.println("What would you like to do? Enter help for commands.");
choice = userInput.next().toLowerCase();
if(choice.equals("go right")) method();
if(choice.equals("go left")) method();
if(choice.equals("go forwards")) method();
if(choice.equals("go backwards")) method();
if(choice.equals("help")) System.out.println("I can print!");
x--;
System.out.println("Value of x: " + x);
}
}
The code above seems to run twice, x is reduced by two before the scanner asks for user input again.
public void method(){
System.out.println("methoding");
}
Additionally, the method doesn't run when called from an if statement but the print statement will.
Your method isn't being called because userInput.next() will only return the next word (ie. until there's a space). You should look into .nextLine() or .useDelimiter() to change this behaviour and return an entire line.
This also explains why x decreases twice -- if you type "go right", that counts as two separate .next()s.
You must add static to method, because now it's an instance method and can't be called from a static function like main.
Don't check x != 0. It's possible it works, but in a complicated loop, where x can reduce more than one time, it may pass 0, go into negatives and never end the loop. Check x > 0 instead.
Use a for loop instead while, if you need to increment/decrement the loop controlling variable at the end of loop.
Related
So I have the following script to get all combination of an array :
'''
var value = new Array(40)
for (var i=0;i<value.length;i++){
value[i]=i;
}
var comb_list = getAllComb(value,24);
trace(comb_list)
function getAllComb(values:Array, r:int):Array{
var n = values.length;
var result = new Array();
var a = new Array(r);
// initialize first combination
for (var i = 0; i < r; i++) {
a[i] = i;
}
i = r - 1; // Index to keep track of maximum unsaturated element in array
// a[0] can only be n-r+1 exactly once - our termination condition!
var count = 0;
while (a[0] < n - r + 1) {
// If outer elements are saturated, keep decrementing i till you find unsaturated element
while (i > 0 && a[i] == n - r + i) {
i--;
}
result.push(a.slice())// pseudo-code to print array as space separated numbers
count++;
a[i]++;
// Reset each outer element to prev element + 1
while (i < r - 1) {
a[i + 1] = a[i] + 1;
i++;
}
}
return result;
}
'''
Running above script will get me:
Error: Error #1502: A script has executed for longer than the default timeout period of 15 seconds.
How to add time delay each 14 seconds passed so that I can run the script? So, after 14 seconds passed, the program will wait for 50ms then continue.
Any help appreciated.
So, there's a simple (well, pretty much so) and working example of how to separate the heavy calculations part from the main thread so the main thread (which also handles UI and external events like user input) would run smoothly, while being able to read the progress and the results of the heavy calculations going under the hood. It also is in a form of a single class, this could be a bit confusing (until you understand how it works) but still easy to handle and modify.
Although the background AVM goes along the same execution flow (code execution > graphics rendering > code execution > graphics rendering > and so on), there are no graphics to render hence there's no need to anyhow limit the code execution time. As a result Worker thread is not a subject to 15 seconds limit, which, somehow, solves the problem.
package
{
import flash.events.Event;
import flash.display.Sprite;
import flash.utils.ByteArray;
import flash.concurrent.Mutex;
import flash.system.Worker;
import flash.system.WorkerDomain;
public class MultiThreading extends Sprite
{
// These variables are needed by both the main and
// subservient threads and will actually point to
// the very same object instances, though from
// the different sides of this application.
private var B:ByteArray;
private var W:Worker;
private var M:Mutex;
// Constructor method.
public function MultiThreading()
{
super();
// This property is 'true' for the main thread
// and 'false' for any Worker instance created.
if (Worker.current.isPrimordial)
{
prepareProgress();
prepareThread();
startMain();
}
else
{
startWorker();
}
}
// *** THE MAIN THREAD *** //
private var P:Sprite;
private var F:Sprite;
// Prepares the progress bar graphics.
private function prepareProgress():void
{
F = new Sprite;
P = new Sprite;
P.graphics.beginFill(0x0000FF);
P.graphics.drawRect(0, 0, 100, 10);
P.graphics.endFill();
P.scaleX = 0;
F.graphics.lineStyle(0, 0x000000);
F.graphics.drawRect(0, 0, 100, 10);
F.x = 10;
F.y = 10;
P.x = 10;
P.y = 10;
addChild(P);
addChild(F);
}
// Prepares the subservient thread and shares
// the ByteArray (the way to pass messages)
// and the Mutex (the way to access the shared
// resources in a multi-thread environment
// without stepping on each others' toes).
private function prepareThread():void
{
M = new Mutex;
B = new ByteArray;
B.shareable = true;
B.writeObject(incomingMessage);
W = WorkerDomain.current.createWorker(loaderInfo.bytes);
W.setSharedProperty("message", B);
W.setSharedProperty("lock", M);
}
// Starts listening to what the background thread has to say
// and also starts the background thread itself.
private function startMain():void
{
addEventListener(Event.ENTER_FRAME, onFrame);
W.start();
}
private var incomingMessage:Object = {ready:0, total:100};
private function onFrame(e:Event):void
{
// This method runs only 20-25 times a second.
// We need to set a lock on the Mutex in order
// to read the shared data without any risks
// of colliding with the thread writing the
// same data at the same moment of time.
M.lock();
B.position = 0;
incomingMessage = B.readObject();
M.unlock();
// Display the current data.
P.scaleX = incomingMessage.ready / incomingMessage.total;
P.alpha = 1 - 0.5 * P.scaleX;
// Kill the thread if it signalled it is done calculating.
if (incomingMessage.terminate)
{
removeEventListener(Event.ENTER_FRAME, onFrame);
W.terminate();
B.clear();
B = null;
M = null;
W = null;
}
}
// *** THE BACKGROUND WORKER PART *** //
// I will use the same W, M and B variables to refer
// the same Worker, Mutex and ByteArray respectively,
// but you must keep in mind that this part of the code
// runs on a different virtual machine, so it is the
// different class instance thus its fields are not
// the same quite as well.
// Initialization.
private function startWorker():void
{
W = Worker.current;
M = W.getSharedProperty("lock");
B = W.getSharedProperty("message");
// Before starting the heavy calculations loop
// we need to release the main thread which is
// presently on W.start() instruction. I tried
// without it and it gives a huuuge lag before
// actually proceeding to intended work.
addEventListener(Event.ENTER_FRAME, onWorking);
}
private function onWorking(e:Event):void
{
removeEventListener(Event.ENTER_FRAME, onWorking);
var aMax:int = 10000000;
// Very very long loop which might run
// over the course of several seconds.
for (var i:int = 0; i < aMax; i++)
{
// This subservient thread does not actually need to
// write its status every single loop, so lets don't
// explicitly lock the shared resources for they
// might be in use by the main thread.
if (M.tryLock())
{
B.position = 0;
B.writeObject({ready:i, total:aMax});
M.unlock();
}
}
// Let's notify the main thread that
// the calculations are finally done.
M.lock();
B.position = 0;
B.writeObject({ready:i, total:aMax, terminate:true});
M.unlock();
// Release the used variables and prepare to be terminated.
M = null;
B = null;
W = null;
}
}
}
The error is not related to your script needing a time delay, the problem is your while loops are making your script unresponsive for more than 15 seconds, triggering the script timeout error. Action Script only allows 15 seconds for your script to execute.
Your first while loop looks problematic, and I'm unclear how the value of a[0] changes to end the loop. Add a break to the loop or make sure the condition changes to allow the loop to end, and you should solve your problem. You can also considering adding continue statements to your embedded while loops if they are only supposed to run one time after they find an unsaturated value.
Personally, since you are using ActionScript, I'd suggest using objects and listeners for value changes instead of iterating over arrays checking for changes.
You could also add a manual timeout for your while loop, but would need to include logic for it to pick up where it left off.
//Set timer to 14 seconds
timeout = getTimer() + 14000;
while(true && timeout > getTimer()){
trace("No Error");
}
If you were used Adobe Animate (Flash), you could change the "Script Time Limit" from Publish setting page.
String color1 = moreColors.get(0);
String color2 = moreColors[0];
System.assertEquals(color1, color2);
// Iterate over a list to read elements
for(Integer i=0;i<colors.size();i++) {
// Write value to the debug log
System.debug(colors[i]);
}
I am learning Apex and just started what is meaning of line System.assertEquals(color1, color2); and what is mean by debug log here?
System.assert, System.assertEquals, System.assertNotEquals. I argue these are three of the most important method calls in Apex.
These are assert statements. They are used in testing to validate that the data you have matches your expectations.
System.assert tests an logical statement. If the statement evaluates to True, the code keeps running. If the statement evaluates to False, the code throws an exception.
System.assertEquals tests that two values are equal. If the two are equal, the code keeps running. If they are not equal, the code throws an exception.
System.assertNotEqual tests that two values are not equal. If the two are not equal, the code keeps running. If they are equal, the code throws an exception.
These are critical for completing system testing. In Apex Code, you must have 75% line test coverage. Many people do this by generating test code that simply covers 75% of their lines of code. However, this is an incomplete test. A good test class actually tests that the code does what you expect. This is really great to ensure that your code actually works. This makes debugging and regression testing far easier. For example. Lets create a method called square(Integer i) that squares the integer returned.
public static Integer square( Integer i ) {
return i * i;
}
A poor test method would simply be:
#isTest
public static void test_squar() {
square( 1 );
}
A good test method could be:
#isTest
public static void test_square() {
Integer i;
Integer ret_square;
i = 3;
ret_square = square( i );
System.assertEquals( i * i; ret_square );
}
How I would probably write it is like this:
#isTest
public static void test_square() {
for( Integer i = 0; i < MAX_TEST_RUNS; i++ ) {
System.assertEquals( i*i, square( i ) );
}
}
Good testing practices are integral to being a good developer. Look up more on Testing-Driven Development. https://en.wikipedia.org/wiki/Test-driven_development
Line by Line ...
//Get color in position 0 of moreColors list using the list get method store in string color1
String color1 = moreColors.get(0);
//Get color in position 0 of moreColors list using array notation store in string color2,
//basically getting the same value in a different way
String color2 = moreColors[0];
//Assert that the values are the same, throws exception if false
System.assertEquals(color1, color2);
// Iterate over a list to read elements
for(Integer i=0;i<colors.size();i++) {
// Write value to the debug log
System.debug(colors[i]);//Writes the value of color list ith position to the debug log
}
If you are running this code anonymously via the Developer console you can look for lines prefixed with DEBUG| to find the statements, for e.g.
16:09:32:001 USER_DEBUG 1|DEBUG| blue
More about system methods can be found at https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_system.htm#apex_System_System_methods
I am trying to apply a method to an array of arrays through a for loop.
Unfortunately where I have inserted my array of arrays inside the checkGuess method, I am getting the error 'Local variable x defined in an enclosing scope must be final or effectively final'. I'm a little new to Java so I'm not sure what I'm doing wrong... any help would be greatly appreciated.
for(int x = 0; x < columns.length; x++){
columns[x][y].addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event) {
checkGuess(columns[x][y]);
}
});
if(x>4 && y<5){
y++;
x=-1;
}
}
Additional info:
The array of arrays contains JButtons.
The method checkGuess() takes a JButton as an argument as so:
checkGuess(JButton guess){
}
In Java, variables that are used in an anonymous class must be final (or in Java 8, effectively final - essentially the same thing, just without the explicit final modifier). As for why this is, Jon Skeet has a very nice answer to this here.
One method of correcting your code is simply to assign x to a final reference, as shown below:
for (int x = 0; x < columns.length; x++) {
final int copy = x;
columns[x][y].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
checkGuess(columns[copy][y]);
}
});
}
ActionListener is an inner anonymous class and it doesn't know what 'x' is when it tries to read it when passing the array of arrays to the function checkGuess().
Untested, but this might work:
for(int x = 0; x < columns.length; x++){
columns[x][y].addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event) {
checkGuess(this);
}
});
if(x>4 && y<5){
y++;
x=-1;
}
}
If not, you would need to find out how to pass x into the class.
I believe "this" will reference the parent of the class, which should be 'columns[x][y]. I could be wrong though.
I am having trouble with the while loop in my code. The instructions say to "Set a loop-control variable to a value that automatically enters the loop for the first time". Any suggestions on how I can do this? Any input will be appreciated. Thank you!
}//end main
I will assume you don't know what most of these terms mean.
A while loop assumes the following syntax (I'll do it in C# since I'm not sure what language you're coding in; update your original post and I'll change my samples):
while (/* loop control/condition here */)
{
// Code here
}
This evaluates like this in english (pseudocode):
while the loop control is true
do this
when it equals false leave the while
So what you want to do is initialize a variable (I'm using type bool here for clarity's sake) and put it in between the parenthesis as the "loop control."
Here's a small sample:
bool daytime = true; // This is the loop control.
int i = 0;
while (daytime == true) // We are seeing if it's day out.
{
System.out.println("It is daytime.");
if (i == 6) {daytime = false;} // If our counter hits 6:00 it's nighttime.
i = i + 1; // Increment our counter.
}
Anyway hope that helps you. Good luck!
Edit: Do-While
I may have misunderstood your original question a bit, this is what a do-while loop looks like:
Syntax:
do
{
// Code here
} while (/* loop control/condition here */);
Pseudocode:
do this code
keep repeating code until the condition is false
Sample:
bool daytime = true; // This is the loop control.
int i = 0;
do
{
System.out.println("It is daytime.");
if (i == 6) {daytime = false;} // If our counter hits 6:00 it's nighttime.
i = i + 1; // Increment our counter.
} while (daytime == true) // We are seeing if it's day out.
Is there a way to continue the most outer loop from the most nested one in ABAP?
Example in Java. There is a construct in this language using labels (most people do not know of it anyway) which allows me to continue the most outer loop from the nested one.
public class NestedLoopContinue {
public static void main(String[] args) {
label1: for (int i = 0; i < 5; i++) {
for (int j = 0; j < 2; j++) {
if (i == 3) {
continue label1;
}
}
System.out.println(i + 1);
}
}
}
This outputs
1
2
3
5
Now, how can I do it in ABAP in a smart way? One solution would be to use TRY. ENDTRY. block but it is rather a hacking one. Any other ideas?
DATA: l_outer_counter TYPE i.
DO 5 TIMES.
l_outer_counter = sy-index.
TRY.
DO 2 TIMES.
IF l_outer_counter = 4.
RAISE EXCEPTION TYPE cx_abap_random.
ENDIF.
ENDDO.
WRITE / l_outer_counter.
CATCH cx_abap_random.
CONTINUE.
ENDTRY.
ENDDO.
Or maybe there is a way to tell whether the DO. ENDO. ended with an EXIT statement (without introducing an own variable of course, like SYST global variable)?
DATA: l_outer_counter TYPE i.
DO 5 TIMES.
l_outer_counter = sy-index.
DO 2 TIMES.
IF l_outer_counter = 4.
EXIT.
ENDIF.
ENDDO.
IF sy-last_loop_ended_with_exit = abap_true. "???
CONTINUE.
ENDIF.
WRITE / l_outer_counter.
ENDDO.
I don't know of an ABAP-specific solution, but I've used a general programming solution to handle this before; simply use a boolean and check at the end of the inner loop whether or not to continue.
In Java:
public class NestedLoopContinue
{
public static void main(String[] args)
{
for (int i = 0; i < 5; i++)
{
boolean earlyBreak = false;
for (int j = 0; j < 2; j++)
{
if (i == 3)
{
earlyBreak = true;
break;
}
}
if (earlyBreak)
{
continue;
}
System.out.println(i + 1);
}
}
}
And in ABAP:
DATA: l_outer_counter type i,
early_break type FLAG.
DO 5 TIMES.
l_outer_counter = sy-index.
DO 2 TIMES.
IF l_outer_counter = 4.
early_break = ABAP_TRUE.
EXIT.
ENDIF.
ENDDO.
IF early_break = ABAP_TRUE.
CLEAR early_break.
CONTINUE.
ENDIF.
WRITE / l_outer_counter.
ENDDO.
I've read that the reason label-based breaks exist in Java in the first place is because GOTO statements explicitly do not, and the case covered by label-based break was one of the few "good" uses of GOTO that the team wanted to maintain.
In general, though, this is a very awkward construction. Is there no potential way to refactor your code (perhaps swapping the inner-ness of the loops) to remove the need for this in the first place?
When working with nested loops, I often find the best way to improve readability, and avoid using more unusual approaches (such as breaking to a label, which is not only controversial because of its goto-like nature, but also reduces readability because a lot of people are not familiar with them) is to extract the inner loop into a separate function. I do not know how this is done in ABAP, but the refactored Java equivalent would be:
public class NestedLoopContinue {
public static void main(String[] args) {
for (int i = 0; i < 5; i++) {
NestedLoopContinue.innerLoop(i)
}
}
static void innerLoop(int i) {
for (int j = 0; j < 2; j++) {
if (i == 3) {
return;
}
}
System.out.println(i + 1);
}
}
I would argue that in this example, this actually becomes less readable because it is harder to follow the logic across the two methods. However, if this was a real-world example (where the methods and variables had some actual meanings and appropriate names to go with them), then the result of extracting the inner loop into a separate method would be more readable than using a label.
Based on the robjohncox answer, the ABAP code might look like this.
CLASS lcl_nested_loop_continue DEFINITION FINAL.
PUBLIC SECTION.
CLASS-METHODS:
main.
PRIVATE SECTION.
CLASS-METHODS:
inner_loop
IMPORTING
i_index TYPE i.
ENDCLASS.
CLASS lcl_nested_loop_continue IMPLEMENTATION.
METHOD main.
DO 5 TIMES.
lcl_nested_loop_continue=>inner_loop( sy-index ).
ENDDO.
ENDMETHOD.
METHOD inner_loop.
DO 2 TIMES.
IF i_index = 4.
RETURN.
ENDIF.
ENDDO.
WRITE / i_index.
ENDMETHOD.
ENDCLASS.