Develop Reference

How to replace String with unicode characters

I intend to replace strings with normal strings into split strings, but there is a difference in length between the normal strings which amounts to 62 and the split length turns out to be 117, so when we write the 'a' button it doesn't change to '𝕒' is there another way of writing replace string easier?
public static String doublestruck(String input){
String normal = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
String split = "𝟘𝟙𝟚𝟛𝟜𝟝𝟞𝟟𝟠𝟡𝕒𝕓𝕔𝕕𝕖𝕗𝕘𝕙𝕚𝕛𝕟𝕠𝕡𝕢𝕣𝕤𝕥𝕦𝕧𝕨𝕩𝕪𝕫𝔸𝔹ℂ𝔻𝔼𝔽𝔾ℍ𝕀𝕁𝕂𝕃𝕄ℕ𝕆ℙℚℝ𝕊𝕋𝕌𝕍𝕎𝕏𝕐ℤ";
String output = "";
char letter;
for(int i = 0; i < input.length(); i++){
letter = input.charAt(i);
int a = normal.indexOf(letter);
output += (a != -1) ? split.charAt(a):letter;
}
return new StringBuilder(output).toString();
}

The letters like 𝟜 (U+1D7DC) are not in the Basic Multilingual Pane and thus take up two char values in Java.
Instead of charAt you need to use codePointAt and to find the correct offset you need to use offsetByCodePoint instead of directly using the same index. So split.charAt(a) needs to be replaced by split.codePointAt(spli.offsetByCodePoint(0, a)).

Convert String into Title Case

I am a beginner in Java trying to write a program to convert strings into title case. For example, if String s = "my name is milind", then the output should be "My Name Is Milind".
import java.util.*;
class TitleCase
{
public static void main(String args[])
{
Scanner in = new Scanner(System.in);
System.out.println("ent");
String s=in.nextLine();
String str ="";
char a ;
for(int i =0;i<s.length()-1;i++)
{
a = s.charAt(i);
if(a==' ')
{
str = str+(Character.toUpperCase(s.charAt(i+1)));
}
else
{
str =str+(Character.toLowerCase(a));
}
}
//for(int i =0; i<s.length();i++)
//{
System.out.println(str);
//}
}
}

You are trying to capitalize every word of the input.
So you have to do following steps:
get the words separated
capitalize each word
put it all together
print it out
Example Code:
public static void main(String args[]){
Scanner in = new Scanner(System.in);
System.out.println("ent");
String s=in.nextLine();
//now your input string is storred inside s.
//next we have to separate the words.
//here i am using the split method (split on each space);
String[] words = s.split(" ");
//next step is to do the capitalizing for each word
//so use a loop to itarate through the array
for(int i = 0; i< words.length; i++){
//we will save the capitalized word in the same place again
//first, geht the character on first position
//(words[i].charAt(0))
//next, convert it to upercase (Character.toUppercase())
//then add the rest of the word (words[i].substring(1))
//and store the output back in the array (words[i] = ...)
words[i] = Character.toUpperCase(words[i].charAt(0)) +
[i].substring(1);
}
//now we have to make a string out of the array, for that we have to
// seprate the words with a space again
//you can do this in the same loop, when you are capitalizing the
// words!
String out = "";
for(int i = 0; i<words.length; i++){
//append each word to out
//and append a space after each word
out += words[i] + " ";
}
//print the result
System.out.println(out);
}

Using Java 8 streams:
String titleCase = (new ArrayList<>(Arrays.asList(inputString.toLowerCase().split(" "))))
.stream()
.map(word -> Character.toTitleCase(word.charAt(0)) + word.substring(1))
.collect(Collectors.joining(" "));

The problem is with the way you're adding characters. Take a look at your if condition:
a = s.charAt(i);
if(a==' ')
{
// Here you are adding not the current character, but the NEXT character.
str = str+(Character.toUpperCase(s.charAt(i+1)));
}
else
{
// Here you are adding the current character.
str =str+(Character.toLowerCase(a));
}
As a result of this condition, you will skip a character if your input string contains a space, then repeat another character that you've already added.
Additionally, you're not looping through the whole string because your loop conditional goes to s.length()-1. Change that to just s.length(). However, if you do that, you may run into an exception if the input string ends with a space (since you'll try to check for a character at an out-of-bound index).
Here's what the fixed code would look like:
public static void main(String args[])
{
Scanner in = new Scanner(System.in);
System.out.println("ent");
String s=in.nextLine();
String str ="";
char a ;
for(int i =0;i<s.length();i++)
{
a = s.charAt(i);
if(a==' ')
{
str = str+Character.toLowerCase(a)+(Character.toUpperCase(s.charAt(i+1)));
i++; // "skip" the next element since it is now already processed
}
else
{
str =str+(Character.toLowerCase(a));
}
}
System.out.println(str);
}
NOTE: I only fixed the code that you supplied. However, I'm not sure it works the way you want it to - the first character of the string will still be whatever case it started in. Your conditional only uppercases letters that are preceded by a space.

You want to change the case of the first letter of each word of a String.
To do so, I would follow the following steps :
split the String in words : see String.split(separator)
retrieve the first letter of each word : see String.charAt(index)
retrieve its capitalized version : the Character.toUpperCase(char) you use is perfect
concatenate the capitalized letter with the rest of the word : concatenation operator (+) and String.substring
create a new String from the capitalized words : see String.join(separator)

Code Golf variation... I challenge anyone to make it any simpler than this:
public String titleCase(String str) {
return Arrays
.stream(str.split(" "))
.map(String::toLowerCase)
.map(StringUtils::capitalize)
.collect(Collectors.joining(" "));
}

By the way: Unicode distinguishes between three cases: lower case, upper case and title case. Although it does not matter for English, there are other languages where the title case of a character does not match the upper case version. So you should use
Character.toTitleCase(ch)
instead of Character.toUpperCase(ch) for the first letter.
There are three character cases in Unicode: upper, lower, and title. Uppercase and lowercase are familiar to most people. Titlecase distinguishes characters that are made up of multiple components and are written differently when used in titles, where the first letter in a word is traditionally capitalized. For example, in the string "ljepotica",[2] the first letter is the lowercase letter lj(\u01C9 , a letter in the Extended Latin character set that is used in writing Croatian digraphs). If the word appeared in a book title, and you wanted the first letter of each word to be in uppercase, the correct process would be to use toTitleCase on the first letter of each word, giving you "Ljepotica" (using Lj, which is \u01C8). If you incorrectly used toUpperCase, you would get the erroneous string "LJepotica" (using LJ, which is \u01C7).
[The Java™ Programming Language, Fourth Edition, by James Gosling, Ken Arnold, David Holmes (Prentice Hall). Copyright 2006 Sun Microsystems, Inc., 9780321349804]

WordUtils.capitalizeFully() worked for me like charm as it gives: WordUtils.capitalizeFully("i am FINE") = "I Am Fine"

import java.util.Scanner;
public class TitleCase {
public static void main(String[] args) {
System.out.println("please enter the string");
Scanner sc1 = new Scanner(System.in);
String str = sc1.nextLine();
//whatever the format entered by user, converting it into lowercase
str = str.toLowerCase();
// converting string to char array for
//performing operation on individual elements
char ch[] = str.toCharArray();
System.out.println("===============");
System.out.println(str);
System.out.println("===============");
//First letter of senetence must be uppercase
System.out.print((char) (ch[0] - 32));
for (int i = 1; i < ch.length; i++) {
if (ch[i] == ' ') {
System.out.print(" " + (char) (ch[i + 1] - 32));
//considering next variable after space
i++;
continue;
}
System.out.print(ch[i]);
}
}
}

You can use lamda instead-
String titalName = Arrays.stream(names.split(" "))
.map(E -> String.valueOf(E.charAt(0))+E.substring(1))
.reduce(" ", String::concat);

Java: Next character in String

I have one String generated of random characters that will encrypt another String given by the user by adding the first character from the String with the first character of the given String. It's working fine, but if the user were to enter multiple words with spaces in between, I want to choose the next character of the first String rather than code the space itself. Is that possible? This is what I have:
(random is the coded string and sentenceUpper is string given by user)
public static void encrypt(String sentenceUpper){
String newSentence = "";
for(int i = 0; i < sentenceUpper.length(); i++){
char one = random.charAt(i);
char two = sentenceUpper.charAt(i);
if(one < 'A' || one > 'Z'){
two = sentenceUpper.charAt(1 + i);}
char result = (char)((one + two)%26 + 'A');
newSentence += "" + result;
}
EDIT FOR BETTER EXPLANATION:
I have:
String random = "WFAZYZAZOHS";
I would like to code user input:
String upperCase: "YOU GO";
So, I'm going to take Y + L = U, etc...
to get :
"UTUSEN
"
But I see that there's a space in "YOU GO" , So I'd like to change it to:
WFA ZY + YOU GO = UTU SE.
I hope that's better explained.

The simplest way to do this would probably be to use an if statement to run the code in the loop only if the character is not a space. If you don't want to skip the character in the random string, you would need a separate variable to track the current character index in that string.
Example: Put this after defining one and two and put the rest of the loop inside it:
if(two==' '){
...
}
Then, add the space in the output:
else{
newSentence+=" ";
}

Formatting String Array efficiently in Java

I was working on some string formatting, and I was curious if I was doing it the most efficient way.
Assume I have a String Array:
String ArrayOne[] = {"/test/" , "/this/is/test" , "/that/is/" "/random/words" }
I want the result Array to be
String resultArray[] = {"test", "this_is_test" , "that_is" , "random_words" }
It's quite messy and brute-force-like.
for(char c : ArrayOne[i].toCharArray()) {
if(c == '/'){
occurances[i]++;
}
}
First I count the number of "/" in each String like above and then using these counts, I find the indexOf("/") for each string and add "_" accordingly.
As you can see though, it gets very messy.
Is there a more efficient way to do this besides the brute-force way I'm doing?
Thanks!

You could use replaceAll and replace, as follows:
String resultArray[] = new String[ArrayOne.length];
for (int i = 0; i < ArrayOne.length; ++i) {
resultArray[i] = ArrayOne[i].replaceAll("^/|/$", "").replace('/', '_');
}
The replaceAll method searches the string for a match to the regex given in the first argument, and replaces each match with the text in the second argument.
Here, we use it first to remove leading and trailing slashes. We search for slashes at the start of the string (^/) or the end of the string (/$), and replace them with nothing.
Then, we replace all remaining slashes with underscores using replace.

Character swapping

I'm trying to swap the first and last character in a string so what I did was I was able to retrieve its first and last characters but am now having hard times putting them all together:
String name="pera";
char[] c = name.toCharArray();
char first = c[0];
char last = c[c.length-1];
name.replace(first, last);
name.replace(last, first);
System.out.println(name);
Although I am getting for the variable 'first' the value of "p" and for the variable 'last' the value of "a", these methods replace() are not turning up with a valid result as the name stays as it is. Does anyone have any idea on how to finish this?

1) String are immutable in Java. so name.replace(first, last) will not modify name but will return a new String.
2) String#replace(char oldChar, char newChar) replaces all occurrences of oldChar in this string with newChar.
For example:
System.out.println("aaaddd".replace("a","d"));
Will give :
dddddd
Possible solution : If you convert your String to a char[], you can easily swap the characters :
public static String inverseFirstAndLast(String str){
char[] c = str.toCharArray();
Character temp = c[0];
c[0] = c[c.length-1];
c[c.length-1]=temp;
return new String(c);
}

Swapping the first with the last is easy like this:
String str = "SwapDemo";
String swapped = str.charAt(str.length() - 1) + str.substring(1, str.length() - 1) + str.charAt(0);
The method you tried will replace all the occurrences of the passed argument, which is not what you want. The code above will do what you want.
As Arnoud pointed out, strings are immutable. But, fixing that issue, you will still get wrong results for:
acbbc
for example

c[0] = last;
c[c.length-1] = first;
System.out.println(new String(c));

Here's a regex based solution:
String str = "demo";
String swapped = str.replaceAll("^(.)(.*)(.)$", "$3$2$1");

Related to solution of #Martijn Courteaux. You can also store the result inside same str String hence saving a little bit of space, like this:
String str = "pera";
String str = str.charAt(str.length() - 1) + str.substring(1, str.length() - 1) + str.charAt(0);