```    1 import java.applet.*;
2 import java.awt.*;
3 import java.awt.event.*;
4 import java.util.StringTokenizer;
5
6 /**
7  * Applet to find prime factorization of an integer
8  * Creation date: (01/29/2002 9:45:40 AM)
9  * Modified date: (04/15/2002 2:52:00 PM)
10  * @author: Andrew Freed, arf132@psu.edu
11  */
12
13 /*
14 Development of this applet was sponsored by the Penn State Fund for
15 Excellence in Learning and Teaching (FELT), project "Java-based
16 Teaching of Mathematics in Information Sciences and Technology",
17 supervised by Frank Ritter and David Mudgett.
18 */
19
20 public class FactorizerApplet extends Applet {
21   private Button btnGo          = new Button();
22   private Label lblAnswer       = new Label("",Label.CENTER);
23   private Label lblInstruction  = new Label("Number to be factored:");
24   private TextField txtStartNum = new TextField("",10);
25   private ScrollPane pneDisplay = new ScrollPane(ScrollPane.SCROLLBARS_AS_NEEDED);
26
27   //The first 669 primes, which go up to 4999
28   private int primes[] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83,
29  89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179,
30  181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271,
31  277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379,
32  383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479,
33  487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599,
34  601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
35  709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823,
36  827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941,
37  947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049,
38  1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151,
39  1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249,
40  1259, 1277, 1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361,
41  1367, 1373, 1381, 1399, 1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459,
42  1471, 1481, 1483, 1487, 1489, 1493, 1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559,
43  1567, 1571, 1579, 1583, 1597, 1601, 1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657,
44  1663, 1667, 1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759,
45  1777, 1783, 1787, 1789, 1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877,
46  1879, 1889, 1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997,
47  1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069, 2081, 2083, 2087, 2089,
48  2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213,
49  2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297, 2309, 2311,
50  2333, 2339, 2341, 2347, 2351, 2357, 2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411,
51  2417, 2423, 2437, 2441, 2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543,
52  2549, 2551, 2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663,
53  2671, 2677, 2683, 2687, 2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741,
54  2749, 2753, 2767, 2777, 2789, 2791, 2797, 2801, 2803, 2819, 2833, 2837, 2843, 2851,
55  2857, 2861, 2879, 2887, 2897, 2903, 2909, 2917, 2927, 2939, 2953, 2957, 2963, 2969,
56  2971, 2999, 3001, 3011, 3019, 3023, 3037, 3041, 3049, 3061, 3067, 3079, 3083, 3089,
57  3109, 3119, 3121, 3137, 3163, 3167, 3169, 3181, 3187, 3191, 3203, 3209, 3217, 3221,
58  3229, 3251, 3253, 3257, 3259, 3271, 3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331,
59  3343, 3347, 3359, 3361, 3371, 3373, 3389, 3391, 3407, 3413, 3433, 3449, 3457, 3461,
60  3463, 3467, 3469, 3491, 3499, 3511, 3517, 3527, 3529, 3533, 3539, 3541, 3547, 3557,
61  3559, 3571, 3581, 3583, 3593, 3607, 3613, 3617, 3623, 3631, 3637, 3643, 3659, 3671,
62  3673, 3677, 3691, 3697, 3701, 3709, 3719, 3727, 3733, 3739, 3761, 3767, 3769, 3779,
63  3793, 3797, 3803, 3821, 3823, 3833, 3847, 3851, 3853, 3863, 3877, 3881, 3889, 3907,
64  3911, 3917, 3919, 3923, 3929, 3931, 3943, 3947, 3967, 3989, 4001, 4003, 4007, 4013,
65  4019, 4021, 4027, 4049, 4051, 4057, 4073, 4079, 4091, 4093, 4099, 4111, 4127, 4129,
66  4133, 4139, 4153, 4157, 4159, 4177, 4201, 4211, 4217, 4219, 4229, 4231, 4241, 4243,
67  4253, 4259, 4261, 4271, 4273, 4283, 4289, 4297, 4327, 4337, 4339, 4349, 4357, 4363,
68  4373, 4391, 4397, 4409, 4421, 4423, 4441, 4447, 4451, 4457, 4463, 4481, 4483, 4493,
69  4507, 4513, 4517, 4519, 4523, 4547, 4549, 4561, 4567, 4583, 4591, 4597, 4603, 4621,
70  4637, 4639, 4643, 4649, 4651, 4657, 4663, 4673, 4679, 4691, 4703, 4721, 4723, 4729,
71  4733, 4751, 4759, 4783, 4787, 4789, 4793, 4799, 4801, 4813, 4817, 4831, 4861, 4871,
72  4877, 4889, 4903, 4909, 4919, 4931, 4933, 4937, 4943, 4951, 4957, 4967, 4969, 4973,
73  4987, 4993, 4999};
74   private int primeArraySize = primes.length;
75
76
77 /**
78  * Function that will factor a given integer
79  */
80     String getFactorization(int myNum)
81     {
82   //Error on negative input
83   if( myNum <= 0 )
84     return "Please select a positive integer to factor";
85
86       String result = new String();
87   result += (intToString(myNum) + " = ");
88
89   //Cycle over all the primes in the list.
90   //Note that we don't have to check primes after a certain point
91   // myNum > primes[idx]*primes[idx] tells us the maximum prime we must check against
92   int idx=0;
93   int numFactors=0;
94   while( myNum >= 1 && idx < primeArraySize && (myNum > primes[idx]*primes[idx]))
95   {
96     while( myNum % primes[idx] == 0 )
97     {
98       //Separate this into a function later
99       result += (intToString(primes[idx]) + " * ");
100       myNum /primes[idx];
101       numFactors++;
102     }
103     idx++;
104   }
105
106   //Add on the last, unfactorable part.  If no factors, precede this with "1 *"
107   if( myNum != 1 )
108   {
109     if( numFactors == 0 )
110       result += "1 * ";
111     result += intToString(myNum);
112   }
113   else
114   {
115     //Get rid of last ' * '
116     result = result.substring(0, result.length() - 3);
117   }
118
119       return result;
120     }
121
122 //This method takes an integer value and converts it to a string with commas placed
123 //every three digits from the right.
124 private String intToString(int myInt)
125 {
126   String result = "";
127   String buf = new Integer(myInt).toString();
128   boolean isNegative = false;
129   int numCommas = 0;
130
131   if( myInt < 0 )
132   {
133     //Truncate sign
134     isNegative = true;
135     buf = buf.substring(1);
136   }
137
138   int len = buf.length();
139
140   //Short case, no commas
141   if( len <= 3 )
142   {
143     if( isNegative )
144       result = "-" + buf;
145     else
146       result = buf;
147
148     return result;
149   }
150
151   //Otherwise place the first comma from the *left*
152   //At each step, remove from the buffer what has been added to the result
153   int firstComma = len % 3;
154   if( firstComma == 0 )
155   {
156     firstComma += 3;
157     result = buf.substring(0, 3) + ",";
158     buf = buf.substring(3);
159   }
160   else
161   {
162     result = buf.substring(0, firstComma) + ",";
163     buf = buf.substring(firstComma);
164   }
165   numCommas++;
166
167   // Truncation of integer division on purpose -- 4, 5, 6 digit numbers each have the
168   // same number of commas
169   while( numCommas < ((len-1) /3) )
170   {
171     result += buf.substring(0, 3) + ",";
172     buf = buf.substring(3);
173     numCommas++;
174   }
175   result += buf;
176
177   //Re-attach the sign if necessary
178   if( isNegative)
179     result = "-" + result;
180
181   return result;
182 }
183
184 //Reads text from a text field while ignoring whitespace and commas
185 //Our use will be to return a string that contains a number
186 private String getText(TextField myText)
187 {
188   String result = "";
189   String buf = myText.getText();
190
191   //Want to pull out commas and spaces from text box
192   StringTokenizer st = new StringTokenizer(buf, " ,\t");
193
194   while( st.hasMoreElements() )
195     result += st.nextToken();
196
197   return result;
198 }
199
200
201 /**
202  * Initializes the applet.
203  */
204 public void init() {
205   try {
206     super.init();
207     setName("FactorizerApplet");
208     setLayout(null);
209     setSize(426, 240);
210       pneDisplay.setBounds(15, 65, 398, 164);
211       lblInstruction.setBounds(22, 18, 139, 23);
212       txtStartNum.setBounds(173, 17, 100, 29);
213       btnGo.setBounds(298, 21, 56, 23);
214       btnGo.setLabel("Go!");
215       btnGo.setActionCommand("btnGo");
217         public void actionPerformed(java.awt.event.ActionEvent e)
218         {
219           makeCall();
220         }
221       });
223         public void actionPerformed(java.awt.event.ActionEvent e)
224         {
225           makeCall();
226         }
227       });
233
234     btnGo.requestFocus();
235     txtStartNum.requestFocus();
236   } catch (java.lang.Throwable Exc) {
237     handleException(Exc);
238   }
239 }
240
241     //Interface function between buttons and actual code
242     //Retrieves value from textbox and sends proper value to code
243     private void makeCall()
244     {
245   try{
246     String strInput = getText(txtStartNum);
247     txtStartNum.setText("");
248
249         if( strInput == null )
251         else
253
254     //Very odd... I can't get the scrollbars to show up
255     //until I do this!
256     pneDisplay.doLayout();
257   }
258   catch(java.lang.NumberFormatException nfe)
259   {
261   }
262     }
263
264
265 /**
266  * Called whenever the part throws an exception.
267  * @param exception java.lang.Throwable
268  */
269 private void handleException(java.lang.Throwable exception) {
270   //Currently exceptions are not handled since the applet does not have
271   //stdout or stderr available to it.
272 }
273
274 // This main function allows you to run this applet as an application
275 /**
276  * main entrypoint - starts the part when it is run as an application
277  * @param args java.lang.String[]
278  */
279 public static void main(java.lang.String[] args) {
280   try {
281     Frame frame = new java.awt.Frame();
282     FactorizerApplet aFactorizerApplet;
283     Class iiCls = Class.forName("FactorizerApplet");
287     frame.setSize(aFactorizerApplet.getSize());
289       public void windowClosing(java.awt.event.WindowEvent e) {
290         System.exit(0);
291       };
292     });
293     frame.show();
294     java.awt.Insets insets = frame.getInsets();
295     frame.setSize(frame.getWidth() + insets.left + insets.right, frame.getHeight() + insets.top + insets.bottom);
296     frame.setVisible(true);
297   } catch (Throwable exception) {
298     System.err.println("Exception occurred in main() of java.applet.Applet");
299     exception.printStackTrace(System.out);
300   }
301 }
302
303 }
304 ```