The use of StringBuffer

/* Thread Safety (multithreading) * Security-sync-data is secure * unsafe-out of sync-more efficient * security and efficiency issues are problems that will haunt us forever. * Security: Hospital website, Bank website * Efficiency: news website, Forum and Other * * StringBuffer: * Thread-safe variable string. * * The difference between StringBuffer and string? * The former is variable in length and content and the latter is immutable. * If you use the former to do string concatenation, will not waste too much resources. * * StringBuffer Construction Method: * Public StringBuffer (): Non-parametric construction method *public StringBuffer (int capacity): Specifies the capacity of the string buffer object *public stringbuf Fer (String str): Specifies the string content of the string buffer object * * StringBuffer method: *public int Capacity (): Returns the current capacity. Theoretical value *public int length (): Returns the length (number of characters). Actual value */public class Stringbufferdemo {public static void main (string[] args) {//Public stringbuffer (): Non-parametric construction method StringBuffer s b = new StringBuffer (); System.out.println ("SB:" + SB); "" System.out.println ("sb.capacity ():" + sb.capacity ());  16system.out.println ("Sb.length ():" + sb.length ()); 0system.out.println ("--------------------------");//public stringbuffer (int capacity): A string buffer object that specifies the capacity stringbuffer SB2 = new StringBuffer (50); System.out.println ("SB2:" + SB2); "" System.out.println ("sb2.capacity ():" + sb2.capacity ()); 50system.oUt.println ("Sb2.length ():" + sb2.length ()); 0system.out.println ("--------------------------");//Public StringBuffer (String str): A string buffer object that specifies the contents of the string StringBuffer SB3 = new StringBuffer ("Hello"); System.out.println ("SB3:" + SB3); HelloSystem.out.println ("Sb3.capacity ():" + sb3.capacity ()); 21system.out.println ("Sb3.length ():" + sb3.length ()); 5}}

/* * stringbuffer Add functionality: * Public stringbuffer Append (string str): Any type of data can be added to the string buffer, and returns the string buffer itself * public stringbuffer Insert (int offset,string str): Inserts any type of data into the string buffer at the specified location and returns the string buffer itself */public class St Ringbufferdemo {public static void main (string[] args) {//Create a string buffer object StringBuffer SB = new StringBuffer ();//public string Buffer Append (String str)//StringBuffer SB2 = sb.append ("Hello");//System.out.println ("SB:" + SB);// System.out.println ("SB2:" + SB2);//System.out.println (SB = = SB2); true//Add Data//Sb.append ("Hello") in step-by-step,//Sb.append (TRUE);//Sb.append (34.56);//Sb.append (+//), chained programming sb.append (" Hello "). Append (True). Append. Append (34.56); System.out.println ("SB:" + SB);//public stringbuffer Insert (int offset,string//str): Inserts any type of data into the string buffer at the specified location, and returns the string buffer itself Sb.insert (5, "World"); System.out.println ("SB:" + SB);}} 

/* * stringbuffer Delete function * public stringbuffer deletecharat (int index): Deletes the character at the specified position and returns itself * Public StringBuffer Delete (int start,int end): Deletes the end of the specified position starting at the specified position and returns itself */public class Stringbufferdemo {public static void Main (string[] args) {//create object StringBuffer SB = new StringBuffer ();//Add function sb.append ("Hello"). Append ("World"). Append ( "Java"); System.out.println ("SB:" + SB);//Public StringBuffer deletecharat (int index): Deletes the character at the specified position and returns itself//demand: I want to delete e this character, swollen?// Sb.deletecharat (1);//demand: I want to delete the first l this character, swollen?//Sb.deletecharat (1);//public StringBuffer Delete (int start,int//end): Deletes the content at the end of the specified position starting at the specified location, and returns itself//requirements: I want to delete the world this string, swollen?//Sb.delete (5, 10);//demand: I want to delete all data sb.delete (0, Sb.length ()); System.out.println ("SB:" + SB);}} 

/* * StringBuffer Replacement function: * Public stringbuffer replace (int start,int end,string str): Replace */public class stri with str from start to end Ngbufferdemo {public static void main (string[] args) {//Create a string buffer object StringBuffer SB = new StringBuffer ();//Add Data Sb.append (" Hello "); Sb.append (" World "); Sb.append (" Java "); System.out.println ("SB:" + SB);//public StringBuffer replace (int start,int end,string//str): From start to end with STR replacement// Requirements: I want to replace the world data with "Happy Holidays" sb.replace (5, 10, "Happy Holidays"); System.out.println ("SB:" + SB);}}

/* * StringBuffer reversal function: * Public stringbuffer reverse () */public class Stringbufferdemo {public static void main (string[] args) {//Create a string buffer object StringBuffer SB = new StringBuffer ();//Add Data sb.append ("Xia Qing lin Love Me"); System.out.println ("SB:" + SB);//public StringBuffer reverse () sb.reverse (); System.out.println ("SB:" + SB);}}

/* * stringbuffer interception function: Note The return value type is no longer stringbuffer itself * public String substring (int start) * Public String substring (int start,int end) */public class Stringbufferdemo {public static void main (string[] args) {//Create Word The string buffer object StringBuffer SB = new StringBuffer ();//add Element Sb.append ("Hello"). Append ("World"). Append ("Java"); System.out.println ("SB:" + SB);//intercept function//public string substring (int start) string s = sb.substring (5); System.out.println ("s:" + s); System.out.println ("SB:" + SB);//public string substring (int start,int end) String ss = Sb.substring (5, 10); SYSTEM.OUT.PRINTLN ("SS:" + ss); System.out.println ("SB:" + SB);}} 

/* * Why do we explain the conversion between classes: * A--B conversion * We convert A to B, actually to use the function of B. * B--a conversion * We may want the result is a type, so we have to turn back. * * String and StringBuffer are converted to each other? */public class Stringbuffertest {public static void main (string[] args) {//String--stringbufferstring s = "Hello";//Note : The value of the string cannot be assigned directly to stringbuffer//stringbuffer sb = "Hello";//StringBuffer SB = s;//Mode 1: By construction method StringBuffer SB = new Stringbuf Fer (s);//Mode 2: Through Append () method StringBuffer SB2 = new StringBuffer (); Sb2.append (s); System.out.println ("SB:" + SB); System.out.println ("SB2:" + SB2); System.out.println ("---------------");//StringBuffer--Stringstringbuffer buffer = new StringBuffer ("Java");// String (stringbuffer buffer)//mode 1: By constructing the method string str = new string (buffer);//Mode 2: Through the ToString () method String str2 = Buffer.tostring (); System.out.println ("str:" + str); System.out.println ("str2:" + str2);}} 

/* * stitching an array into a string */public class StringBufferTest2 {public static void main (string[] args) { Define an array int[] arr = {44, 33, 55, 11, 22};//define the function//mode 1: String to stitch the way string S1 = arraytostring (arr); System.out.println ("S1:" + S1);//Mode 2: The way to do stitching with stringbuffer string s2 = arrayToString2 (arr); System.out.println ("s2:" + s2);} Use StringBuffer to make stitching public static String arrayToString2 (int[] arr) {StringBuffer sb = new StringBuffer (); Sb.append ("["  ), for (int x = 0, x < Arr.length, + +) {if (x = = arr.length-1) {sb.append (arr[x]),} else {sb.append (arr[x]). Append (", ");}} Sb.append ("]"); return sb.tostring ();} Use String to stitch the public static string arraytostring (int[] arr) {string s = ""; s + = "["; for (int x = 0; x < arr.length; X + +) {if (× = = Arr.length-1) {s + = arr[x];} else {s + = Arr[x];s + = ",";}} s + = "]"; return s;}} 

import java.util.scanner;/* * Reverse string */public class StringBufferTest3 {public static void Main (string[] args) {//keyboard input data Scanner sc = new Scanner (system.in); System.out.println ("Please enter data:"); string s = Sc.nextline ();//mode 1: string concatenation string S1 = Myreverse (s); System.out.println ("S1:" + S1);//Mode 2: Reverse () function with stringbuffer string s2 = MyReverse2 (s); System.out.println ("s2:" + s2);} Use StringBuffer's reverse () function public static String MyReverse2 (String s) {//StringBuffer SB = new StringBuffer ();//Sb.appen D (s);//StringBuffer SB = new StringBuffer (s);//Sb.reverse ();//return sb.tostring ();//Simple version return new StringBuffer (s). Re Verse (). toString ();} Use String to stitch public static string Myreverse (string s) {string result = ""; char[] CHS = S.tochararray (); for (int x = Chs.le Ngth-1; x >= 0; x--) {//char ch = chs[x];//result + = Ch;result + chs[x];} return result;}} 

Import java.util.scanner;/* * Determine if a string is a symmetric string * For example "ABC" is not a symmetric string, "ABA", "ABBA", "AAA", "MNANM" is a symmetric string * * Analysis: * Determine if a string is a symmetric word String, I just need to compare * First and last comparison * Second and penultimate comparison * ... * the number of comparisons is the length divided by 2. */public class StringBufferTest4 {public static void main (string[] args) {//Create keyboard Entry Object Scanner sc = new Scanner (system.in); S Ystem.out.println ("Please enter a string:"); String s = sc.nextline ();//One of the comparison Boolean B = Issame (s); System.out.println ("B:" + b);//inverse function with string buffers Boolean b2 = IsSame2 (s); System.out.println ("B2:" +B2);} public static Boolean isSame2 (String s) {return new StringBuffer (s). Reverse (). ToString (). Equals (s); public static Boolean Issame (string s) {/////convert string to character array//char[] CHS = S.tochararray ();////for (int start = 0, end = Chs.length-1; Start <= end; start++, end--) {//if (Chs[start]! = Chs[end]) {//return false;//}//}////return true;//}public static Boolean Issame (String s) {Boolean flag = true;//The string to a character array char[] CHS = S.tochararray (); for (int start = 0, end = chs.length-1; start <= end; Start+ +, end--) {if (Chs[start]! = Chs[end]) {flag = False;break;}} return flag;}}

/* * Interview Question: * 1:string,stringbuffer,stringbuilder difference? * A:string content is immutable, and stringbuffer,stringbuilder is content-changeable. * B:stringbuffer is synchronous, data security, low efficiency; StringBuilder is unsynchronized, data insecure, high efficiency * * 2:stringbuffer and array differences? * Both can be seen as a container, loaded with other data. * But, StringBuffer's data is ultimately a string of data. * While arrays can place a variety of data, they must be of the same data type. * * 3: Formal Parameter Problem * string passed as parameter * StringBuffer as parameter * * Formal parameter: * Basic type: Change of formal parameter does not affect actual parameter * Reference type: Change of formal parameter directly affects actual parameter * * NOTE: * stri Ng is passed as a parameter, and the effect and the base type are passed as arguments. */public class Stringbufferdemo {public static void main (string[] args) {String S1 = "Hello"; String s2 = "World"; SYSTEM.OUT.PRINTLN (S1 + "---" + s2);//Hello---worldchange (s1, S2); SYSTEM.OUT.PRINTLN (S1 + "---" + s2);//Hello---worldstringbuffer sb1 = new StringBuffer ("Hello"); StringBuffer SB2 = new StringBuffer ("World"); System.out.println (SB1 + "---" + sb2);//Hello---worldchange (sb1, SB2);  System.out.println (SB1 + "---" + sb2);//Hello---worldworld}public static void Change (StringBuffer sb1, StringBuffer SB2) {SB1 = Sb2;sb2.append (SB1);} public static void Change (StrinG S1, String s2) {S1 = S2;s2 = s1 + s2;}} 

The use of StringBuffer