string-concatenation

问题 I wonder if there is a better (i.e. faster execution) solution to the problem described below. Step 1) create table t (k number, v1 number, v2 number); insert into t values (1,1,1); insert into t values (1,2,2); insert into t values (1,2,3); insert into t values (1,3,3); insert into t values (1,4,3); insert into t values (2,7,8); insert into t values (2,7,9); Step 2) I would like to return the following data set (k, v1_list, v2_list) 1, (1,2,3,4), (1,2,3) 2, (7), (8,9) Step 3) I am able to

问题 I'm working in Java and I've got the following method: public ResultSet getRecordsWithinBoundingBox(int spillFarLeftValue, int spillFarRightValue, int spillMostDownwardValue, int spillMostUpwardValue) { ResultSet resultSet = null; try { Statement statement = dbConnection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE); String sql = "SELECT * FROM OTH WHERE (jl<=" + spillMostUpwardValue + " AND (ih>=" + spillFarLeftValue + " AND ih<=" + spillFarRightValue+ ") OR

问题 I am trying to concatenate 4 strings in Prolog. I am able to concatenate 2 and 3 strings but I can't get it to work with 4. This is what I have so far: join2(String1,String2,Newstring) :- name(String1,L1), name(String2,L2), append(L1,L2,Newlist), name(Newstring,Newlist). join3(String1,String2,String3,Newstring) :- join2(String1,String2,S), join2(S,String3,Newstring). join4(String1,String2,String3,String4,Newstring) :- join3(String1,String2,String3,Newstring), join2(String1,String2,S), join2(S

问题 What I'm referring to is concatenating String s with a certain String in the middle, such as concatenating sentences separated by a period, or parameter lists with a comma. I know you can use libraries, but sometimes these can't do what you want, like when you want to generate the phrases you are concatenating. So far I've come up with two solutions, StringBuffer sentence = new StringBuffer(); String period = ""; for ( int i = 0; i < sentences.length; i++ ) { sentence.append( period +

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . Which is below method is faster when combining 2 strings ? And why can it run faster? PHP code: $str1 = 'Hello'; $str2 = 'World';

问题 I have several lists of strings like so, from a possible list of several dozen: 1: { "A", "B", "C" } 2: { "1", "2", "3" } 3: { "D", "E", "F" } These three were only picked as an example, and the user can pick from several dozen similar lists with varying number of elements. For another example, this is also a perfectly valid selection for a user: 25: { } // empty 4: { "%", "!", "$", "@" } 16: { "I", "a", "b", "Y" } 8: { ")", "z", "!", "8" } What I want to do is get every combination of

问题 I have a cell array of numeric strings e.g.: labels = {'1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12'} I'm trying to add a string ( 'Label ' ) to the beginning of each array element without using any kind of loop, as the array is massive and I need the code to run quickly. My other requirement is the space after the word 'Label' must be maintained once I apply it to the two-digit elements in the array. The result I want is: fullLabels = {'Label 1', 'Label 2', 'Label 3', 'Label

问题 I know that in more recent Java versions string concatenation String test = one + "two"+ three; Will get optimized to use a StringBuilder . However will a new StringBuilder be generated each time it hits this line or will a single Thread Local StringBuilder be generated that is then used for all string concatenation? In other words can I improve on the performance for a frequently called method by creating my own thread local StringBuilder to re-use or will there be no significant gains by

问题 Does C# do any compile-time optimization for constant string concatenation? If so, how must my code by written to take advantage of this? Example: How do these compare at run time? Console.WriteLine("ABC" + "DEF"); const string s1 = "ABC"; Console.WriteLine(s1 + "DEF"); const string s1 = "ABC"; const string s2 = s1 + "DEF"; Console.WriteLine(s2); 回答1: Yes, it does. You can verify this using by using ildasm or Reflector to inspect the code. static void Main(string[] args) { string s = "A" + "B

问题 The plus ( + ) operator and String.concat() method gives the same result. plus ( + ) operator ; str1 + str2; String concat() method ; str1.concat(str2); Addionally, it is written in w3schools ; But with JavaScript, methods and properties are also available to primitive values, because JavaScript treats primitive values as objects when executing methods and properties. So which way is better to use to combine for either we use on primitives or on String objects in JS, what are the performance