Create the Set

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// Create the set

Set set = new HashSet();

// Add elements to the set

set.add("a");

set.add("b");

set.add("c");

// Remove elements from the set

set.remove("c");

// Get number of elements in set

int size = set.size(); // 2

// Adding an element that already exists in the set has no effect

set.add("a");

size = set.size(); // 2

// Determining if an element is in the set

boolean b = set.contains("a"); // true

b = set.contains("c"); // false

// Iterating over the elements in the set

Iterator it = set.iterator();

while (it.hasNext()) {

// Get element

Object element = it.next();

}

Method Summaryboolean add(Object o)

Adds the specified element to this set if it is not already present (optional operation)

boolean addAll(Collection c)

Adds all of the elements in the specified collection to this set if they're not alreadypresent (optional operation).

void clear()

Removes all of the elements from this set (optional operation).

boolean contains(Object o)

Returns true if this set contains the specified element.

boolean containsAll(Collection c)

Returns true if this set contains all of the elements of the specified collection.

boolean equals(Object o)

Compares the specified object with this set for equality.

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int hashCode()

Returns the hash code value for this set.

boolean isEmpty()

Returns true if this set contains no elements.

Iterator iterator()Returns an iterator over the elements in this set.

boolean remove(Object o)

Removes the specified element from this set if it is present (optional operation).

boolean removeAll(Collection c)

Removes from this set all of its elements that are contained in the specifiedcollection (optional operation).

boolean retainAll(Collection c)

Retains only the elements in this set that are contained in the specified collection

(optional operation).int size()

Returns the number of elements in this set (its cardinality).

Object[] toArray()

Returns an array containing all of the elements in this set.

Object[] toArray(Object[] a)

Returns an array containing all of the elements in this set; the runtime type of thereturned array is that of the specified array.

What is the type of the objects in your

arrays? You want compare the object'svalue or just the object(the reference)

itself?EmptyStackAug 29 '11 at 10:47

both arrays contains strings, I want to put common strings to a new

arraysajazAug 29 '11 at 10:55

Alright. Try this solution.stackoverflow.com/questions/7207805/

EmptyStackAug 29 '11 at 10:58

@Vijay you copied your own answer and you link to it. Wouldn't be

one enough?vikingosegundoAug 29 '11 at 11:17

@viking just now i answered for both of them.by read from his comments i

realize that he has nsstring in both.so that i have route him to that link.butbefore that i had thought any object he wants.nothing

elseAppleVijayAug 29 '11 at 11:21

compare

SArray *array1 = [[NSArray alloc] initWithObjects:@"a",@"b",@"c",nil];

NSArray *array2 = [[NSArray alloc] initWithObjects:@"a",@"d",@"c",nil];

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NSMutableArray *ary_result = [[NSMutableArray alloc] init];

for(int i = 0;i

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frequency[i] = 0 ;}

o 7Step through each value in your data set, adding one to the frequency array element

corresponding to that value. The index corresponding to the current value is generated byshifting the value by the minimum value.for (i = 0 ; i < numvalues ; i++) {int index = values[i] - minval ;frequency[index]++ ;}

o 8Step through each element in the frequency array. Print the current value (calculated byshifting the iterator "i" by the minimum value). Print the number of stars (*) corresponding tothe frequency the current value by looping from one to the value stored in the frequencyarray, printing a single star each time.

for (i = 1 ; i

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h.put("NY", "New York");h.put("RI", "Rhode Island");h.put("BC", "British Columbia");

// look up a key in the HashtableString key = "NY";String stateName = (String)h.get(key );System.out.println(stateName );

// prints "New York"

// enumerate all the contents of the hashtableEnumeration keys = h.keys();

while (keys.hasMoreElements()) { key = (String)keys.nextElement(); stateName = (String)h.get(key ); System.out.println(key + " "+ stateName ); // prints lines of the form NY New York // in effectively random order. }// end while

Histogram.java

Below is the syntax highlighted version ofHistogram.java from 3.2 Creating

Data Types.

/

***********************************************************************

**

* Compilation: javac Histogram.java

*

* This data type supports simple client code to create dynamic

* histograms of the frequency of occurrence of values in [0, N).

* The frequencies are kept in an instance-variable array, and

* an instance variable max tracks the maximum frequency (for

scaling).

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*

* % java Histogram 50 1000000

*

**********************************************************************

***/

publicclass Histogram {

privatefinaldouble[] freq; // freq[i] = # occurences of value i

privatedouble max; // max frequency of any value

// Create a new histogram.

publicHistogram(int N) {

freq =newdouble[N];

}

// Add one occurrence of the value i.

publicvoidaddDataPoint(int i) {

freq[i]++;

if(freq[i]> max) max = freq[i];

}

// draw (and scale) the histogram.

publicvoiddraw() {

StdDraw.setYscale(0, max);

StdStats.plotBars(freq);

}

// See Program 2.2.6.

publicstaticvoidmain(String[] args) {

int N = Integer.parseInt(args[0]); // number of coins

int T = Integer.parseInt(args[1]); // number of trials

// create the histogram

Histogram histogram =newHistogram(N+1);

for(int t =0; t < T; t++) {

histogram.addDataPoint(Bernoulli.binomial(N));

}

// display using standard draw

StdDraw.setCanvasSize(500,100);

histogram.draw();

}

}

Copyright 20002010, Robert Sedgewick and Kevin Wayne.Last updated: Wed Feb 9 09:07:43 EST 2011.

Histogram printing program

import javax.swing.*;

public class Histogram

{

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public static void main( String args[] )

{

int n[] = { 19, 3, 15, 7, 11, 9, 13, 5, 17, 1 };String output = "";

output += "Element\tValue\tHistogram";

for ( int i = 0; i < n.length; i++ )

{output += "\n" + i + "\t" + n[ i ] + "\t";

for ( int j = 1; j

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JavaRanch Java Forums Java Beginning Java

Author

Displaying a histogram using input fro

array

kanaka tamRanch Hand

Joined: Jan 19,

2004Posts: 42

posted Friday, April 15, 2005 23:02

Hello folks,

I am currently working on a problem that inputs 20 numbers into an array and the n

range of 0 to 100. I had to calculate smallest, largest, mean and average of all the n

which i was able to do without any problem. But the second half of the problem is to

show how many numbers are in the ranges of 0 to 9, 10 to 19 etc., This is a class as

read the instructions ofjava ranch. So i just need a little head start and not expectin

me. This is how far i have gotten with the code.

view plaincopy to clipboardprint?

1. import java.awt.*;

2. import java.applet.*;3.

4.

5. publicclass ArrayTest extends Applet

6.7. {

8. privateint [] num = {5, 7, 8, 19, 25, 30, 37, 41, 43, 50, 52, 55

9. 61, 63, 70, 76, 84, 91, 95, 98};10.

11.

12. privateint max, min, sum;

13. privatefloat average;14.

15. publicvoid largestSmallest()16. {

17.

18. max = -1;

19. min = 101;20.

21. for (int i = 0; i < num.length; i++)22. {

23. if (max < num[i])24. {

25. max = num[i];

26. }

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27. if (min > num[i])28. {

29. min = num[i];

30. }

31. }

32.

33. }34.

35. publicvoid sumAverage()36. {

37. sum = 0;

38. average = 0.0f;39.

40. for (int i = 0; i < num.length; i++)41. {

42. sum = sum + num[i];

43. average = (float)(sum) / num.length;44. }

45.

46. }47.

48.

49.

50. publicvoid paint (Graphics g)51. {

52. largestSmallest();

53. sumAverage();

54.

55. g.drawString("The largest number in this array is: " + max, 30

56. g.drawString("The smallest number in this array is: " + min,

57. g.drawString("The sum of the numbers in this array is: " + s

58. g.drawString("The mean of the numbers in this array is: " + av59.60.

61. }

62.

63. }

64.

I am lost in figuring out how to do the histogram for this problem. Any help appreciat

know how to approach this portion of the problem,

Thanx,

kt

Ryan McGuireRanch Hand

Joined: Feb 18,2005

Posts: 864

posted Saturday, April 16, 2005 01:14

Make the histogram in two steps:

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1. Collect the numbers into some data structure (most likely an array).

2. Output the results.

Are you supposed to use something like System.out.println() to output a row of aster

or do you have to do something more graphical?

Ryan

kanaka tamRanch Hand

Joined: Jan 19,2004

Posts: 42

posted Saturday, April 16, 2005 02:09

Originally posted by Ryan McGuire:

Make the histogram in two steps:

1. Collect the numbers into some data structure (most likely an array).

2. Output the results.

Are you supposed to use something like System.out.println() to output a row of asterisks

you have to do something more graphical?

Ryan

Thank you Ryan. I might have to use an array to collect the range say 0 to 9, 10 to 1

recently introduced to arrays and i don't know how to initialize arrays for a range of n

I am thinking like this, but not sure

private int [] output = {0 - 9, 10 - 19, 20 - 29, 30 - 39, 40 - 49, 50 - 59, 60 - 69, 70

99};

Then if this format is right i have to figure out where my 20 numbers that i have inpu

array exists, that is in what range. I have to use filled rectangles to get a histogram t

many numbers are in the range 0 to 9, 10 to 19 etc.,

How would i check what number is in what range. I know the procedure but not sure

Help appreciated..

kanaka

Ryan McGuire posted Saturday, April 16, 2005 02:27

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Ranch Hand

Joined: Feb 18,

2005Posts: 864

(edit: remove quote)

That array declaration may cause you some trouble. 0-9 = -9. 10-19 = -9, etc. So yo

position array with each position initialized to negative nine.

I think it would be better if you initialized your array to all zeros. And then go throug

numbers and increment one of the ints in output.

Given any input number in the range [0, 99], can you give me an expression or a me

which int in output to increment? For example, if you see a 22, you want to incremen

sure the expression or method works for input numbers that are near the ends of you

and 30.)

Ryan

[ April 15, 2005: Message edited by: Ryan McGuire ]

kanaka tamRanch Hand

Joined: Jan 19,

2004Posts: 42

posted Saturday, April 16, 2005 06:32

Originally posted by Ryan McGuire:

(edit: remove quote)

That array declaration may cause you some trouble. 0-9 = -9. 10-19 = -9, etc. So you'll e

array with each position initialized to negative nine.

I think it would be better if you initialized your array to all zeros. And then go through you

and increment one of the ints in output.

Given any input number in the range [0, 99], can you give me an expression or a method

int in output to increment? For example, if you see a 22, you want to increment output[2]

expression or method works for input numbers that are near the ends of your ranges, suc

Ryan

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[ April 15, 2005: Message edited by: Ryan McGuire ]

Thanx Ryan,

I added the following, no compilation errors but cannot see any histogram output. Co

am i doing wrong. Here is the code.view plaincopy to clipboardprint?

1.

2. import java.awt.*;

3. import java.applet.*;4.

5.

6. publicclass ArrayTest extends Applet7.8. {

9. privateint [] num = {5, 7, 8, 19, 25, 30, 37, 41, 43, 50, 52, 55

10. 61, 63, 70, 76, 84, 91, 95, 98};

11. privateint [] hist = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};12.

13.

14. privateint max, min, sum;

15. privatefloat average;16.

17. publicvoid largestSmallest()18. {

19.

20. max = -1;

21. min = 101;22.

23. for (int i = 0; i < num.length; i++)24. {

25. if (max < num[i])26. {

27. max = num[i];

28. }

29. if (min > num[i])30. {

31. min = num[i];

32. }33. }

34.

35. }

36.

37. publicvoid sumAverage()38. {

39. sum = 0;

40. average = 0.0f;

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41.

42. for (int i = 0; i < num.length; i++)43. {

44. sum = sum + num[i];

45. average = (float)(sum) / num.length;46. }

47.48. }

49.

50. publicvoid drawHist()51. {

52. for( int i = 0; i

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93.

94. g.drawString("The largest number in this array is: " + max, 10

95. g.drawString("The smallest number in this array is: " + min,

96. g.drawString("The sum of the numbers in this array is: " + s

97. g.drawString("The mean of the numbers in this array is: " + av

98.99. int x = 20;

100. int y = 20;

101. int height = 40;102.

103.

104. for(int i = 0; i < hist.length; i++)105. {

106. drawHist();

107. int width = hist[i];

108. g.fillRect(x, y, width * 10, height);109.

110. }

111. x = x + 10;112. }

113.

114. }

115.

I would appreciate any help.

thanx,

kt

subject: Displaying a histogram using input from an array

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Yes, there does seem to be 3rd libraries (none in Java Math). Two that have come up are:

http://opsresearch.com/app/

http://www.iro.umontreal.ca/~simardr/ssj/indexe.htmlbut, it is actually not that difficult to write your own methods to calculate mean, median, mode

and range.

MEAN

publicstaticdouble mean(double[] m) {

double sum = 0;

for (int i = 0; i < double.length; i++) {

sum += m[i];

}

return sum / double.length;

}

MEDIAN

// the array double[] m MUST BE SORTED

publicstaticdouble median(double[] m) {

int middle = m.length/2;

if(m.length%2 == 1) {

return m[middle];

} else {

return (m[middle-1] + m[middle]) / 2.0;

}}

MODE

publicstaticint mode(int a[]) {

int maxValue, maxCount;

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for (int i = 0; i < a.length; ++i) {

int count = 0;

for (int j = 0; j < a.length; ++j) {

if(a[j] == a[i]) ++count;

}

if(count > maxCount) {maxCount = count;

maxValue = a[i];

}

}

return maxValue;

}