Dark Horse Programmer (Java) common class for----API (advanced operation of arrays, regular expressions)

------Java Training, Android training, iOS training,. NET training, look forward to communicating with you! ------- advanced operation of the 4.7 array 4.7.1 Sort 1. Bubble sort

Adjacent elements 22 comparison, large back, the first time, the maximum value appears at the maximum index.

Import Java.awt.image.bufferstrategy;public class ArrayDemo2 {public static void main (string[] args) {//define an array int[] arr = {24, 69, 80, 57, 13}; System.out.println ("Pre-sort:");p Rintarray (arr); Bubblesort (arr); System.out.println ("After sorting:");p Rintarray (arr);} Bubble sort public static void Bubblesort (int[] arr) {for (int x = 0;x<arr.length-1;x++) {for (int y = 0;y<arr.length-1-x;y+ +) {if (arr[y]>arr[y+1]) {int temp = Arr[y];arr[y] = arr[y+1];arr[y+1] = temp;}}} Traverse function public static void PrintArray (int[] arr) {System.out.print ("["); for (int x=0;x<arr.length;x++) {if (x== arr.length-1) {System.out.print (arr[x]);} Else{system.out.print (arr[x]+ "");}} System.out.println ("]");}}

Operation Result:

2. Select Sort

Starting with the 0 index, and then comparing the following elements, small forward, the first time, the minimum value appears at the minimum index.

public class ArrayDemo2 {public static void main (string[] args) {//define an array int[] arr = {24, 69, 80, 57, 13}; System.out.println ("Pre-sort:");p Rintarray (arr); Selectsort (arr); System.out.println ("After sorting:");p Rintarray (arr);} Select sort public static void Selectsort (int[] arr) {for (int x = 0; x < arr.length-1; + +) {for (int y = x; y < ARR.L Ength-1; y++) {if (Arr[x] > arr[y + 1]) {int temp = arr[x];arr[x] = arr[y + 1];arr[y + 1] = temp;}}} Traverse function public static void PrintArray (int[] arr) {System.out.print ("["); for (int x = 0; x < arr.length; X + +) {if (x = = arr.length-1) {System.out.print (arr[x]),} else {System.out.print (arr[x] + ",");}} System.out.println ("]");}}

Operation Result:

Exercise: Sort the characters in a string. "DACGEBF"--"ABCDEFG"

public class Arraytest {public static void main (string[] args) {String s = "DACGEBF"; char[] CHS = S.tochararray ();//BUBBL Esort (CHS); Selectsort (CHS); s = string.valueof (CHS); System.out.println (s);} Bubble sort public static void Bubblesort (char[] CHS) {for (int x = 0; x < chs.length-1; + +) {for (int y = 0; y < chs. Length-1-X; y++) {if (Chs[y] > chs[y + 1]) {Char temp = chs[y];chs[y] = chs[y + 1];chs[y + 1] = temp;}}} Select sort public static void Selectsort (char[] CHS) {for (int x = 0; x < chs.length-1; + +) {for (int y = x; y < chs. Length-1; y++) {if (Chs[x] > chs[y + 1]) {Char temp = chs[x];chs[x] = chs[y + 1];chs[y + 1] = temp;}}}}

Operation Result:

4.7.22-Point lookup (for ordered arrays)

public class Arraydemo {public static void main (string[] args) {//define an array int[] arr = {11,22,33,44,55,66,77};//write function implementation int Inde x = GetIndex (arr, 33); System.out.println ("index:" +index);//What happens if this element does not exist? index = GetIndex (arr, 333); System.out.println ("index:" +index);  /* * Two explicit: * return value type: int * parameter list: int[] arr,int value */public static int getindex (int[] arr,int value) {//define maximum index, minimum index int max = Arr.length-1;int min = 0;//calculates the intermediate index int mid = (max +min)/2;//compares the values of the intermediate index and the value to find while (Arr[mid]! = value) {if (arr[mid]>val UE) {max = mid-1;} else if (arr[mid]<value) {min = mid + 1;} Add to Judge if (Min > Max) {return-1;} Mid = (max +min)/2;} return mid;}}

Operation Result:

4.7.3 Arrays

This class contains various methods for manipulating arrays, such as sorting and searching.

/* * Arrays: A tool class for manipulating arrays. such as sorting and finding. * 1:public static string toString (int[] a) turns the array into a string * 2:public static void sort (int[] a) sorts the arrays * 3:public static int bin Arysearch (int[] a,int key) binary lookup */public class Arraysdemo {public static void main (string[] args) {//define an array int[] arr = { };//public static string toString (int[] a) turns the array into a string System.out.println ("before sorting:" + arrays.tostring (arr)); /public static void sort (int[] a) sorts the array arrays.sort (ARR); System.out.println ("After sorting:" + arrays.tostring (arr));//public static int BinarySearch (int[] a,int key) binary lookup//[13, 24, 57, 6 9, 80]system.out.println ("BinarySearch:" +arrays.binarysearch (arr, 80));}}

Operation Result:

4.8 Regular Expressions

A regular expression uses a single string to describe and match a series of strings that conform to a certain syntactic rule.

4.8.1 rules for regular expressions

4.8.2 Regular expression judgment function

public boolean matches (string regex) method in the String class

Import java.util.scanner;/* * Check QQ number: * Requires 1:5-15 digits * requires 2:0 can not start * Analysis: * 1, keyboard input QQ number * 2, write a function to achieve check * 3, call function, output results */public CLA SS RegexDemo2 {public static void main (string[] args) {//Create keyboard object Scanner sc = new Scanner (system.in); System.out.println ("Please enter your QQ:"); String QQ = Sc.nextline (); System.out.println (CHECKQQ (QQ));} public static Boolean CHECKQQ (String qq) {//String regex = "[1-9][0-9]{4,14}";////public Boolean matches (string regex) informs this Whether the string matches the given regular expression//Boolean flag = Qq.matches (regex);//Return flag;//return Qq.matches ("[1-9][0-9]{4,14}"); return Qq.matches ("[1-9]\\d{4,14}");}}

Operation Result:

Exercise 1: Determine if a mobile phone number conforms to the rules

/* * Judgment Function *string class public boolean matches (String regex) * * Requirements: * Determine if the mobile phone number meets the requirements?  *  * Analysis: * A: Keyboard input mobile phone number * B: Define the mobile phone number rules * 13436975980 * 13688886868 * 13866668888 * 13456789012 * 13123456789 * 18912345678 * 18886867878 * 18638833883 * C: Call function, Judge can * D: output result *  rule: 11 digits * Start with 1 * Second digit is 3 or 8 */public class Regexdemo {public St atic void Main (string[] args) {//keypad input data Scanner sc = new Scanner (system.in); System.out.println ("Please enter the phone number to be judged:"); String phonenumber = Sc.nextline ();//define Cell phone number rule string regex = "1[38]\\d{9}";//Call Rule to determine Boolean flag = Phonenumber.matches (regex); System.out.println ("flag:" +flag);}}

Operation Result:

Exercise 2: Verifying a mailbox

/* * Check mailbox *  Analysis: * A: Keyboard Entry Email * B: Define the rules of the mailbox * [email protected] * [email protected] * [email protected] * [email protecte d] * [email protected] * C: Call function, Judge can * D: Output */public class Regextest {public static void main (string[] args) {//Keyboard entry Mailbox SC Anner sc = new Scanner (system.in); System.out.println ("Please enter e-mail:"); String email = sc.nextline ();//define the mailbox rule//string regex = "[A-za-z_0-9][email protected][a-za-z_0-9]{2,6} (\\.[ a-za-z_0-9]{2,3}) + "; String regex = "\\[email protected]\\w{2,6} (\\.\\w{2,3}) +";//Invoke function Boolean flag = email.matches (regex); System.out.println ("flag:" +flag);}}

Operation Result:

4.8.3 the segmentation function of regular Expressions

Public string[] Split (String regex) method in the String class

Import java.util.scanner;/* * Split function *string class public string[] Split (string regex) * Splits this string based on the match of the given regular expression. *  Example: * Lily net, Century Jia Yuan, cherish the net, QQ * Search Friends * Gender: Female * Range: "18-24" *  * age>=18 && age<=24 */public class Regexdem o {public static void main (string[] args) {//define an age search range string ages = "18-24";//define a rule String regex = "-";//Call method string[] Strar Ray = Ages.split (regex);//traverse//for (int x=0;x <strarray.length;x++) {//system.out.println (strarray[x]);//}// How do I get the int type? int startage = Integer.parseint (strarray[0]), int endage = Integer.parseint (strarray[1]);//keyboard input data Scanner sc = new Scanner (system.in); System.out.println ("Please enter your Age:"); int = Sc.nextint (); if (ages >=startage&&age<=endage) { System.out.println ("You are what I Want");} Else{system.out.println ("You're not what I'm looking for");}}

Operation Result:

Exercise 3:

public class RegexDemo2 {public static void main (string[] args) {//defines a string S1 = "AA,BB,CC"; string[] Str1array = S1.split (","); for (int x = 0; x <str1array.length;x++) {System.out.println (str1array[x]);} System.out.println ("---------------"); String s2 = "aa.bb.cc"; string[] Str2array = s2.split ("\ \"); for (int x = 0; x <str1array.length;x++) {System.out.println (str1array[x]);} System.out.println ("---------------"); String s3 = "AA  bb          cc"; string[] Str3array = s3.split ("+"); for (int x = 0; x <str1array.length;x++) {System.out.println (str1array[x]);} System.out.println ("---------------");//The path on the hard disk, we should use \ \ instead of string s4 = "F:\\java second quarter \\day14\\code\\day14_Regex\\src\\ Cn\\itcast_03 "; string[] Str4array = S4.split ("\\\\"); for (int x = 0; x <str1array.length;x++) {System.out.println (str1array[x]);} System.out.println ("---------------");}}

Operation Result:

Exercise 4:

/* * I'm like the next string: "91 27 46 38 50" * Please write code to achieve the final output is: "27 38 46 50 91" * * Analysis: * A: Define a String * B: Divide the string to get an array of strings * C: Transform the string array into int array * D: Sort int array * E: the sorted int array is assembled into a string * F: Output string */public class Regextest {public static void main (string[] args) {// Define a character string string s = "91 27 46 38 50";//Divide the string into string[] Strarray = S.split ("");//Convert the string array to an int array int[] arr = new Int[strarr ay.length];for (int x = 0; x < arr.length; × x + +) {Arr[x] = Integer.parseint (Strarray[x]);} Sorts an int array bubblesort (arr);//seceltsort (arr);//the sorted int array is assembled into a string/*string result = ""; for (int x = 0; x < arr.length; X + +) {String str = string.valueof (arr[x]); result + = Str;result + = "";} */stringbuilder sb = new StringBuilder (); for (int x = 0;x <arr.length;x++) {sb.append (arr[x]). Append (""); String result = sb.tostring (). Trim (); SYSTEM.OUT.PRINTLN (result);} Bubble sort public static void Bubblesort (int[] arr) {for (int x = 0; x < arr.length-1; + +) {for (int y = 0; y < arr.l Ength-1-X; y++) {if (Arr[y] > arr[y + 1]) {iNT TEMP = Arr[y];arr[y] = arr[y + 1];arr[y + 1] = temp;}}}} 

Operation Result:

4.8.4 the replacement function of regular expressions

public string ReplaceAll of the String class (String regex,string replacement)

/* * Replace function * Public  string ReplaceAll of String class (String regex,string replacement) *  using the given replacement Replace this string with all substrings that match the given regular expression.  */public class Regexdemo {public static void main (string[] args) {//define a string s = "hello1234worldkh6212260502006 823456 ";//I want to remove all the numbers, replace the string regex with" * "=" \\d "; String SS = "*"; String result = S.replaceall (regex, SS); SYSTEM.OUT.PRINTLN (result);}}

Operation Result:

4.8.5 the acquisition function of regular expressions

Use of the pattern class and the Matcher class

/* Get function: * Get the three-character word in the following String * da Jia ting wo shuo,jin tian Yao xia yu,bu Shang wan zi Xi,gao xing bu? */public class RegexDemo2 {public static void main (string[] args) {//define string s = "da Jia ting wo shuo,jin Tian Yao Xi A yu,bu shang wan zi Xi,gao xing bu?; /rule string regex = "\\b\\w{3}\\b";//compile the rule into pattern object pattern P = pattern.compile (regex);//Get Match object by pattern object Matcher m = P.matcher (s) ///Call the function of the match//find the sub-sequence that has not met//public Boolean find ()/* Boolean flag = M.find () by the Find method; SYSTEM.OUT.PRINTLN (flag); How do I get a value? Public * string Group () string ss = M.group (); SYSTEM.OUT.PRINTLN (ss); *  flag = M.find (); ss = M.group (); SYSTEM.OUT.PRINTLN (ss); */while (M.find ()) {System.out.println (M.group ());} Note: Be sure to first find () before group ()//Illegalstateexception:no match found//String ss = M.group ();//SYSTEM.OUT.PRINTLN (ss);}}

Operation Result:

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Dark Horse Programmer (Java) common class for----API (advanced operation of arrays, regular expressions)