This is the code which should generate 6 columns but instead generating 5.
Please point out any logical error in the code due to which desired output cannot be obtained.
sem1Data= new String[18];
sem2Data= new String[18];
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
int stdA = 0, stdB = 0;
int counter = 0;
int colCounter = 1;
LabName = editText.getText().toString();
setLabRef = database.getReference("/" + LabName);
String colName;
for (int i = 0; i <6; i++) {
colName = "col" + colCounter;
//Toast.makeText(Activity1.this, colCounter, Toast.LENGTH_SHORT).show();
if ( colCounter%2 == 0) {
for ( ; stdB<18; stdB++)
{
if(counter<6)
{
setLabRef.child(colName).child(String.valueOf(counter)).setValue(sem2Data[stdB]);
counter++;
}
else
{
counter=0;
colCounter++;
break;
}
}
}
else {
for ( ; stdA<18; stdA++)
{
if (counter<6){
setLabRef.child(colName).child(String.valueOf(counter)).setValue(sem1Data[stdA]);
counter++;
}
else {
counter=0;
colCounter++;
break;
}
}
}
}
}
});
The expected result should be 6 generated columns in firebase but instead only five are generated.
firebase screenshot
In first loop change validation block to i <=6 or i < 7
for( int i = 0; i <= 6; i++)
UPD:
if(counter<7)
I'm not sure what is the purpose of your code but here is my opinion , it might help you to clear things out.
if you will add the line Log.d(TAG, "Log track : stdB : " + stdB +" stdA : " +stdA); At the beginning of your for-loop , you will see that the values of stdA and stdB never set to zero in they just keep increasing according to the logic of your code , actually the both end with the values :
Log track : stdB : 12 stdA : 18
now , if you will look at the case where colCounter = 5 , i = 4 the value of stdA is 12
.
Thats mean that the for-loop at the else section will run (colCounter mod 2 is not zero) only 6 times and by that will not execute:
else
{
counter=0;
colCounter++;
break;
}
and by that you are missing the increase of colCounter from 5 to 6 .
I am getting an error, while calculating on String,
java.lang.StringIndexOutOfBoundsException: length=4; regionStart=5; regionLength=2
My implementation is below.
private void initializeMyPLsAllotted() {
int theMonthWhenICame = Integer.parseInt(myDateHired.substring(5, 7)); //This line is showing the error
int theYearWhenICame = Integer.parseInt(myDateHired.substring(0,4));
int theCurrentMonth = Integer.parseInt(todaysDate.substring(5, 7));
int theCurrentYear = Integer.parseInt(todaysDate.substring(0, 4));
int myTotalMonths = (theCurrentYear - theYearWhenICame)*12 + theCurrentMonth - theMonthWhenICame;
if (myTotalMonths > 6) {
numberOfPLsAllotted = 2;
} else {
numberOfPLsAllotted = 0;
}
myPLs = numberOfPLsAllotted;
}
java.lang.StringIndexOutOfBoundsException: length=4; regionStart=5; regionLength=2
it clearly says that length of your string is 4 and you are trying to fetch sub-string from index 5. make sure your string is valid
you can check something like that to avoid crashing your app
private void initializeMyPLsAllotted() {
if(myDateHired.length() > 7 && todaysDate.length() > 7){
int theMonthWhenICame = Integer.parseInt(myDateHired.substring(5, 7));
int theYearWhenICame = Integer.parseInt(myDateHired.substring(0,4));
int theCurrentMonth = Integer.parseInt(todaysDate.substring(5, 7));
int theCurrentYear = Integer.parseInt(todaysDate.substring(0, 4));
int myTotalMonths = (theCurrentYear - theYearWhenICame)*12 + theCurrentMonth - theMonthWhenICame;
if(myTotalMonths>6) {
numberOfPLsAllotted = 2;
} else {
numberOfPLsAllotted = 0;
}
myPLs = numberOfPLsAllotted;
} else {
// print some error message
}
}
StringIndexOutOfBoundsException means that the section you're trying to substring is outside of the string length.
Example
String test = "123";
String testSubstringOne = test.substring(0, 1);
//testSubstringOne -> "1"
String testSubstringTwo = test.substring(0, 5);
//testSubstringTwo -> java.lang.StringIndexOutOfBoundsException
Make sure your myDateHired has the value you expect.
Tip from the coach
You say that those values are from a server... Maybe you should look into returning data in a more friendly format such as json.
As doc says, the IndexOutOfBoundsException will be throwed when：
if the beginIndex is negative, or endIndex is larger than the length
of this String object, or beginIndex is larger than endIndex
so check myDateHired before using it.
I saw many questions about this, and tried to solve the problem, but after one hour of googling and a lots of trial & error, I still can't fix it. I hope some of you catch the problem.
This is what I get:
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.ComparableTimSort.mergeHi(ComparableTimSort.java:835)
at java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:453)
at java.util.ComparableTimSort.mergeForceCollapse(ComparableTimSort.java:392)
at java.util.ComparableTimSort.sort(ComparableTimSort.java:191)
at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)
at java.util.Arrays.sort(Arrays.java:472)
at java.util.Collections.sort(Collections.java:155)
...
And this is my comparator:
#Override
public int compareTo(Object o) {
if(this == o){
return 0;
}
CollectionItem item = (CollectionItem) o;
Card card1 = CardCache.getInstance().getCard(cardId);
Card card2 = CardCache.getInstance().getCard(item.getCardId());
if (card1.getSet() < card2.getSet()) {
return -1;
} else {
if (card1.getSet() == card2.getSet()) {
if (card1.getRarity() < card2.getRarity()) {
return 1;
} else {
if (card1.getId() == card2.getId()) {
if (cardType > item.getCardType()) {
return 1;
} else {
if (cardType == item.getCardType()) {
return 0;
}
return -1;
}
}
return -1;
}
}
return 1;
}
}
Any idea?
The exception message is actually pretty descriptive. The contract it mentions is transitivity: if A > B and B > C then for any A, B and C: A > C. I checked it with paper and pencil and your code seems to have few holes:
if (card1.getRarity() < card2.getRarity()) {
return 1;
you do not return -1 if card1.getRarity() > card2.getRarity().
if (card1.getId() == card2.getId()) {
//...
}
return -1;
You return -1 if ids aren't equal. You should return -1 or 1 depending on which id was bigger.
Take a look at this. Apart from being much more readable, I think it should actually work:
if (card1.getSet() > card2.getSet()) {
return 1;
}
if (card1.getSet() < card2.getSet()) {
return -1;
};
if (card1.getRarity() < card2.getRarity()) {
return 1;
}
if (card1.getRarity() > card2.getRarity()) {
return -1;
}
if (card1.getId() > card2.getId()) {
return 1;
}
if (card1.getId() < card2.getId()) {
return -1;
}
return cardType - item.getCardType(); //watch out for overflow!
You can use the following class to pinpoint transitivity bugs in your Comparators:
/**
* #author Gili Tzabari
*/
public final class Comparators
{
/**
* Verify that a comparator is transitive.
*
* #param <T> the type being compared
* #param comparator the comparator to test
* #param elements the elements to test against
* #throws AssertionError if the comparator is not transitive
*/
public static <T> void verifyTransitivity(Comparator<T> comparator, Collection<T> elements)
{
for (T first: elements)
{
for (T second: elements)
{
int result1 = comparator.compare(first, second);
int result2 = comparator.compare(second, first);
if (result1 != -result2)
{
// Uncomment the following line to step through the failed case
//comparator.compare(first, second);
throw new AssertionError("compare(" + first + ", " + second + ") == " + result1 +
" but swapping the parameters returns " + result2);
}
}
}
for (T first: elements)
{
for (T second: elements)
{
int firstGreaterThanSecond = comparator.compare(first, second);
if (firstGreaterThanSecond <= 0)
continue;
for (T third: elements)
{
int secondGreaterThanThird = comparator.compare(second, third);
if (secondGreaterThanThird <= 0)
continue;
int firstGreaterThanThird = comparator.compare(first, third);
if (firstGreaterThanThird <= 0)
{
// Uncomment the following line to step through the failed case
//comparator.compare(first, third);
throw new AssertionError("compare(" + first + ", " + second + ") > 0, " +
"compare(" + second + ", " + third + ") > 0, but compare(" + first + ", " + third + ") == " +
firstGreaterThanThird);
}
}
}
}
}
/**
* Prevent construction.
*/
private Comparators()
{
}
}
Simply invoke Comparators.verifyTransitivity(myComparator, myCollection) in front of the code that fails.
It also has something to do with the version of JDK.
If it does well in JDK6, maybe it will have the problem in JDK 7 described by you, because the implementation method in jdk 7 has been changed.
Look at this:
Description: The sorting algorithm used by java.util.Arrays.sort and (indirectly) by java.util.Collections.sort has been replaced. The new sort implementation may throw an IllegalArgumentException if it detects a Comparable that violates the Comparable contract. The previous implementation silently ignored such a situation. If the previous behavior is desired, you can use the new system property, java.util.Arrays.useLegacyMergeSort, to restore previous mergesort behaviour.
I don't know the exact reason. However, if you add the code before you use sort. It will be OK.
System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");
Consider the following case:
First, o1.compareTo(o2) is called. card1.getSet() == card2.getSet() happens to be true and so is card1.getRarity() < card2.getRarity(), so you return 1.
Then, o2.compareTo(o1) is called. Again, card1.getSet() == card2.getSet() is true. Then, you skip to the following else, then card1.getId() == card2.getId() happens to be true, and so is cardType > item.getCardType(). You return 1 again.
From that, o1 > o2, and o2 > o1. You broke the contract.
if (card1.getRarity() < card2.getRarity()) {
return 1;
However, if card2.getRarity() is less than card1.getRarity() you might not return -1.
You similarly miss other cases. I would do this, you can change around depending on your intent:
public int compareTo(Object o) {
if(this == o){
return 0;
}
CollectionItem item = (CollectionItem) o;
Card card1 = CardCache.getInstance().getCard(cardId);
Card card2 = CardCache.getInstance().getCard(item.getCardId());
int comp=card1.getSet() - card2.getSet();
if (comp!=0){
return comp;
}
comp=card1.getRarity() - card2.getRarity();
if (comp!=0){
return comp;
}
comp=card1.getSet() - card2.getSet();
if (comp!=0){
return comp;
}
comp=card1.getId() - card2.getId();
if (comp!=0){
return comp;
}
comp=card1.getCardType() - card2.getCardType();
return comp;
}
}
I had the same symptom. For me it turned out that another thread was modifying the compared objects while the sorting was happening in a Stream. To resolve the issue, I mapped the objects to immutable temporary objects, collected the Stream to a temporary Collection and did the sorting on that.
The origin of this exception is a wrong Comparator implementation. By checking the docs, we must implement the compare(o1, o2) method as an equivalence relation by following the rules:
if a.equals(b) is true then compare(a, b) is 0
if a.compare(b) > 0 then b.compare(a) < 0 is true
if a.compare(b) > 0 and b.compare(c) > 0 then a.compare(c) > 0 is true
You may check your code to realize where your implementation is offending one or more of Comparator contract rules. If it is hard to find it by a static analysis, you can use the data which cast the exception to check the rules.
If you try to run this code you will meet the kind this exception:
public static void main(String[] args) {
Random random = new Random();
List<Integer> list = new ArrayList<>();
for (int i = 0; i < 50000; i++) {
list.add(random.nextInt());
}
list.sort((x, y) -> {
int c = random.nextInt(3);
if (c == 0) {
return 0;
}
if (c == 1) {
return 1;
}
return -1;
});
}
Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.TimSort.mergeLo(TimSort.java:777)
at java.util.TimSort.mergeAt(TimSort.java:514)
at java.util.TimSort.mergeCollapse(TimSort.java:441)
at java.util.TimSort.sort(TimSort.java:245)
at java.util.Arrays.sort(Arrays.java:1512)
at java.util.ArrayList.sort(ArrayList.java:1462)
at Test.main(Test.java:14)
The reason is when implementing the Comparator, it may meet the case of A > B and B > C and C > A and the sort method will be run around to be broken. Java prevent this case by throw exception this case:
class TimSort<T> {
.
.
.
else if (len1 == 0) {
throw new IllegalArgumentException(
"Comparison method violates its general contract!");
.
.
.
In conclusion, to handle this issue. You have to make sure the comparator will not meet the case of A > B and B > C and C > A.
I got the same error with a class like the following StockPickBean. Called from this code:
List<StockPickBean> beansListcatMap.getValue();
beansList.sort(StockPickBean.Comparators.VALUE);
public class StockPickBean implements Comparable<StockPickBean> {
private double value;
public double getValue() { return value; }
public void setValue(double value) { this.value = value; }
#Override
public int compareTo(StockPickBean view) {
return Comparators.VALUE.compare(this,view); //return
Comparators.SYMBOL.compare(this,view);
}
public static class Comparators {
public static Comparator<StockPickBean> VALUE = (val1, val2) ->
(int)
(val1.value - val2.value);
}
}
After getting the same error:
java.lang.IllegalArgumentException: Comparison method violates its general contract!
I changed this line:
public static Comparator<StockPickBean> VALUE = (val1, val2) -> (int)
(val1.value - val2.value);
to:
public static Comparator<StockPickBean> VALUE = (StockPickBean spb1,
StockPickBean spb2) -> Double.compare(spb2.value,spb1.value);
That fixes the error.
I ran into a similar problem where I was trying to sort a n x 2 2D array named contests which is a 2D array of simple integers. This was working for most of the times but threw a runtime error for one input:-
Arrays.sort(contests, (row1, row2) -> {
if (row1[0] < row2[0]) {
return 1;
} else return -1;
});
Error:-
Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.base/java.util.TimSort.mergeHi(TimSort.java:903)
at java.base/java.util.TimSort.mergeAt(TimSort.java:520)
at java.base/java.util.TimSort.mergeForceCollapse(TimSort.java:461)
at java.base/java.util.TimSort.sort(TimSort.java:254)
at java.base/java.util.Arrays.sort(Arrays.java:1441)
at com.hackerrank.Solution.luckBalance(Solution.java:15)
at com.hackerrank.Solution.main(Solution.java:49)
Looking at the answers above I tried adding a condition for equals and I don't know why but it worked. Hopefully we must explicitly specify what should be returned for all cases (greater than, equals and less than):
Arrays.sort(contests, (row1, row2) -> {
if (row1[0] < row2[0]) {
return 1;
}
if(row1[0] == row2[0]) return 0;
return -1;
});
A variation of Gili's answer to check if the comparator satisfies the requirements described in the compare method's javadoc - with a focus on completeness and readability, e.g. by naming the variables the same as in the javadoc. Note that this is O(n^3), only use it when debugging, maybe just on a subset of your elements, in order to be fast enough to finish at all.
public static <T> void verifyComparator(Comparator<T> comparator, Collection<T> elements) {
for (T x : elements) {
for (T y : elements) {
for (T z : elements) {
int x_y = comparator.compare(x, y);
int y_x = comparator.compare(y, x);
int y_z = comparator.compare(y, z);
int x_z = comparator.compare(x, z);
// javadoc: The implementor must ensure that sgn(compare(x, y)) == -sgn(compare(y, x))
if (Math.signum(x_y) == -Math.signum(y_x)) { // ok
} else {
System.err.println("not holding: sgn(compare(x, y)) == -sgn(compare(y, x))" //
+ " | x_y: " + x_y + ", y_x: " + y_x + ", x: " + x + ", y: " + y);
}
// javadoc: The implementor must also ensure that the relation is transitive:
// ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0.
if (x_y > 0 && y_z > 0) {
if (x_z > 0) { // ok
} else {
System.err.println("not holding: ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0" //
+ " | x_y: " + x_y + ", y_z: " + y_z + ", x_z: " + x_z + ", x: " + x + ", y: " + y + ", z: " + z);
}
}
// javadoc: Finally, the implementor must ensure that:
// compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z.
if (x_y == 0) {
if (Math.signum(x_z) == Math.signum(y_z)) { // ok
} else {
System.err.println("not holding: compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z" //
+ " | x_y: " + x_y + ", x_z: " + x_z + ", y_z: " + y_z + ", x: " + x + ", y: " + y + ", z: " + z);
}
}
}
}
}
}
I had to sort on several criterion (date, and, if same date; other things...). What was working on Eclipse with an older version of Java, did not worked any more on Android : comparison method violates contract ...
After reading on StackOverflow, I wrote a separate function that I called from compare() if the dates are the same. This function calculates the priority, according to the criteria, and returns -1, 0, or 1 to compare(). It seems to work now.
What about doing something simpler like this:
int result = card1.getSet().compareTo(card2.getSet())
if (result == 0) {
result = card1.getRarity().compareTo(card2.getRarity())
}
if (result == 0) {
result = card1.getId().compareTo(card2.getId())
}
if (result == 0) {
result = card1.getCardType().compareTo(card2.getCardType())
}
return result;
You just need to order the comparisons in order of preference.
hi i have problem in displaying a value into my TextView..
For example i will input 1,2,3,4 then i like to display the output in this manner in my TextView..How can i do that? please help me, thank you in advance
1 appeared 1 times
2 appeared 1 times
3 appeared 1 times
4 appeared 1 times
here's my code:
String []values = ( sum.getText().toString().split(","));
double[] convertedValues = new double[values.length];
Arrays.sort(convertedValues);
int i=0;
int c=0;
while(i<values.length-1){
while(values[i]==values[i+1]){
c++;
i++;
}
table.setText(values[i] + " appeared " + c + " times");
c=1;
i++;
if(i==values.length-1)
table.setText(values[i] + " appeared " + c + " times");
Make your textView to support multipleLines and after that create in code a StringBuffer and append to it the results, something like
resultString.append(result).append(" appeared").append(c).append(" times\n");
after that you set text for textView like:
textView.setText(resultString.toString());
Here is the idea :
// this is test string, you can read it from your textView
String []values = ( "2, 1, 3, 5, 1, 2".toString().split(","));
int [] intValues = new int[values.length];
// convert string values to int
for (int i = 0; i < values.length; ++i) {
intValues[i] = Integer.parseInt(values[i].trim());
}
// sort integer array
Arrays.sort(intValues);
StringBuilder output = new StringBuilder();
// iterate and count occurrences
int count = 1;
// you don't need internal loop, one loop is enough
for (int i = 0; i < intValues.length; ++i) {
if (i == intValues.length - 1 || intValues[i] != intValues[i + 1]) {
// we found end of "equal" sequence
output.append(intValues[i] + " appeared " + count + " times\n");
count = 1; // reset count
} else {
count++; // continue till we count all equal values
}
}
System.out.println(output.toString()); // prints what you extected
table.setText(output.toString()); // display output
i feel dumb for asking this but i have been fighting with this for a day now and i can't seem to get it working.
So my problem is I want to keep adding 1 to and integer and make it go like ;
1+1=2
2+1=3
That it keeps updating the Integer I have this now;
int val = 1;
int g = 1;
val = g + val;
But it keeps saying its 2 how come?
Thanks.
I'm guessing you put all of your code in your click handler. Instead, put the variable declaration/initialization in the class level and only your addition code in your click handler. Rough code as follows:
public YourActivity extends Activity {
int val = 1;
int g = 1;
#Override
protected void onCreate (Bundle savedInstanceState) {
... //find button in here
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
val = g + val;
}
});
}
}
Because you keep setting it to 1. Initialize it outside the loop.
int val = 1;
int g = 1;
The next line:
val = g + val;
is therefore equivalent to
val = 1 + 1;
which is equivalent to
val = 2;
Not sure what you would expect here...
int val = 1; int g = 1; val = g + val;
Will always evaluate to 2. Because what happens is you take the value in g which is 1 and the value in val which is 1. This produces the sum of 2. You then take 2 and assign it to the variable val (which previously was initialized to 1).
1+1 will always be 2 (in Integer mathematics)
So my problem is I want to keep adding 1 to and integer and make it go like ;
1+1=2
2+1=3
I'm guessing you want to do something like this, to produce your output a given number of times.
int timesToLoop = 10;
int summedUp = 0;
for (int i=0; i < timesToLoop; i++)
{
summedUp = i + 1;
System.out.println(i + " + " + "1 = " + summedUp);
}