Java job 05 (Chapter 1 Common runtime Class 2)

Package homework05; </P> <p> Import Java. math. biginteger; </P> <p> public class ch07_3 {<br/> Public static double factorial (int n) // calculate the factorial function <br/>{< br/> If (n = 0) return 1; <br/> else return N * factorial (n-1 ); <br/>}< br/> Public static biginteger factorial (int n) {<br/> biginteger bigint = NULL; <br/> If (n = 0) {<br/> bigint = new biginteger ("1"); <br/> return bigint; <br/>}</P> <p> else {<br/> bigint = ne W biginteger (integer. tostring (n); <br/> return bigint. multiply (factorial (n-1); <br/>}</P> <p> Public static void main (string [] ARGs) {<br/>/* 4. Calculate 1 + 2! + 3! + 4! + · Sum of items from 100th to 200 */<br/> double f = 0; <br/> for (int K = 100; k <= 200; k ++) {<br/> F + = factorial (k); <br/>}< br/> system. out. println ("1 + 2! + 3! + 4! + · Sum of items from 100th to 200: "+ F); // the output value is infinity <br/> // infinity indicates positive infinity, that is, the value is greater than the maximum value of the double type. Negative infinity outputs-infinity. <br/> // In fact, any calculation result that exceeds the maximum value that can be expressed by the double type produces this result. <Br/> // use a large integer for processing. <Br/> biginteger result = new biginteger ("0"); <br/> for (int K = 100; k <= 200; k ++) {<br/> result = result. add (factorial (k); <br/>}< br/> system. out. println ("1 + 2! + 3! + 4! + · The sum of items from 100th to 200: "+ result); <br/>}</P> <p>

Result:

1 + 2! + 3! + 4! + · Sum of items from 100th to 200: infinity
1 + 2! + 3! + 4! + · Sum of items from 100th to 200: 792621072814943158937574954417696054502273470568077747007887743862285047941581535541498718312275086275679893343076013862361579680670972527976009279036348551929550827607601145450876014530359530008733947699274904382825444692112993342058966668017369617374101405221613980910401559347844227172278387932925351155828685624342954436057587785914951951445917696000000000000000000000000

Whether the question is correct or not remains to be verified.

 

Package homework05; </P> <p> Import Java. util. hashset; <br/> Import Java. util. iterator; </P> <p>/* <br/> * Subject: Set A = {1, 2, 4} and B = {1, 3, 7, 9, 11 }, write an application to output the intersection of A and B, and set and difference set. <Br/> */<br/> public class ch07_4 {</P> <p> Public static void displayset (hashset <integer> temp) {<br/> iterator <integer> iter = temp. iterator (); <br/> while (ITER. hasnext () {<br/> integer TE = (integer) ITER. next (); <br/> system. out. print (Te. intvalue () + "/t"); <br/>}< br/> system. out. println (); // line feed. <Br/>}</P> <p> Public static void main (string [] ARGs) {<br/> integer [] A = {1, 2, 4 }; <br/> integer [] B = {1, 3, 7, 9, 11}; <br/> hashset <integer> A = new hashset <integer> (); <br/> hashset <integer> B = new hashset <integer> (); <br/> for (INT I = 0; I <. length; I ++) {// initialize set a <br/>. add (A [I]); <br/>}< br/> for (INT I = 0; I <B. length; I ++) {// initialize Set B <br/> B. add (B [I]); <br/>}</P> <p> hashset <integer> tempset = (hashset <integer>). CLON E (); // saves the original value of set a as an intermediate variable. </P> <p>. addall (B); // Union <br/> system. out. print ("output result of the union of A and B:"); <br/> displayset (a); // output result. </P> <p> A = (hashset <integer>) tempset. clone (); <br/>. retainall (B); // intersection <br/> system. out. print ("output result of intersection A and B:"); <br/> displayset (a); // output result. </P> <p> A = (hashset <integer>) tempset. clone (); <br/>. remove (B); // intersection <br/> system. out. print ("output result of difference set A and B:"); <br/> displayset (a); // output result. </P> <p >}< br/>

Running result:

Output the result of the union of A and B: 1 2 3 4 7 9 11
Output the result of intersection A and B: 1 3
Output the result of A and B difference sets: 1 2 3 4

Package homework05; </P> <p> Import Java. util. iterator; <br/> Import Java. util. treeset; </P> <p>/* <br/> * Title: 10 hard disks, two important attributes: price and capacity. Write an application and use the <br/> * treemap <K, V> class to sort and output the detailed information of 10 hard disks by price and capacity. <Br/> */<br/> // hard disk class <br/> class harddisk implements comparable {<br/> private int price; <br/> private int content; </P> <p> Public static int flag = 1; // flag is arranged by price or by capacity. 1: price 2: Capacity </P> <p> Public harddisk (INT price, int content) {<br/> This. price = price; <br/> This. content = content; <br/>}< br/> Public int compareto (object B) {<br/> harddisk Hd = (harddisk) B; <br/> If (flag = 1) {<br/> return (this. price-hd.price); <br/>}< br/> If (flag = 2) {<br/> return (this. content-hd.content); <br/>}< br/> return 0; <br/>}</P> <p> Public int getcontent () {<br/> return content; <br/>}< br/> Public void Setcontent (INT content) {<br/> This. content = content; <br/>}< br/> Public int getprice () {<br/> return price; <br/>}< br/> Public void setprice (INT price) {<br/> This. price = price; <br/>}</P> <p >}< br/> public class ch07_5 {</P> <p> Public static void main (string [] ARGs) {<br/> harddisk [] HDS = {New harddisk (), new harddisk ), <br/> New harddisk (150,30), n EW harddisk (500,200), new harddisk (), new harddisk (), <br/> New harddisk (), new harddisk )}; </P> <p> treeset <parddisk> treeset = new treeset <parddisk> (); <br/> for (INT I = 0; I <HDS. length; I ++) {// sort by price by default. <Br/> treeset. add (HDS [I]); <br/>}< br/> iterator <parddisk> iter = treeset. iterator (); <br/> system. out. println ("=== details ="); <br/> system. out. println ("price/T capacity"); <br/> while (ITER. hasnext () {<br/> harddisk Hd = ITER. next (); <br/> system. out. println (HD. getprice () + "/t" + HD. getcontent (); <br/>}</P> <p> // <br/> treeset. clear (); // clear the content in the treeset. <Br/> for (INT I = 0; I <HDS. length; I ++) {// sort by capacity. <Br/> harddisk. flag = 2; <br/> treeset. add (HDS [I]); <br/>}< br/> iterator <parddisk> iter2 = treeset. iterator (); <br/> system. out. println ("=== details ="); <br/> system. out. println ("capacity/t price"); <br/> while (iter2.hasnext () {<br/> harddisk Hd = iter2.next (); <br/> system. out. println (HD. getcontent () + "/t" + HD. getprice (); <br/>}</P> <p >}< br/>

Running result:

=== Details ===
Price capacity
25 1
40 2
80 25
100 35
150 30
200 40
250 38
270 60
300 50
500 200
=== Details ===
Capacity price
1 25
2 40
25 80
30 150
35 100
38 250
40 200
50 300
60 270
200 500