I have a program that reads an input (a String) and prints that String reversed. Now, I need to read through the reversed String and replace all of the "A"s with "T"s, the "T"s with "A"s, the "G"s with "C"s and the "C"s to "G"s. So basically, the "complement". I tried to use multiple lines with a replace function but once the "A"s are turned into "T"s, it will replace all of those into "A"s so there are no "T"s at all. How can I replace the characters so that they do not override each other?
Here is my code if it helps! I don't have any functions to get the "complement" yet, but here is what I'm working with.
import java.util.*;
public class DNA {
public static void main(String[] args)
{
System.out.println("Please input a DNA sequence: ");
Scanner read;
read = new Scanner(System.in);
String input = read.next();
String reverse="";
for(int i = input.length() - 1; i >= 0; i--) {
reverse = reverse + input.charAt(i);
}
System.out.println("Here is the reversed sequence: ");
System.out.println(reverse);
}
}
You can convert your reverse string to a char array like this:
char[] charArr = reverse.toCharArray();
Then you can iterate through it and change the characters that you want:
for(int i = 0; i < charArr.length; i++){
if(charArr[i] == 'A'){
charArr[i] = 't';
}
}
At the end you can convert the char array back to a string like this:
String str = new String(charArr);
Here is a code sample that you can try:
import java.util.Scanner;
class DNA {
public static void main(String[] args)
{
System.out.println("Please input a DNA sequence: ");
Scanner read = new Scanner(System.in);
String input = read.next();
String reverse="";
StringBuilder sb = new StringBuilder();
for(int i = input.length() - 1; i >= 0; i--) {
reverse = reverse + input.charAt(i);
}
for (char c: input.toCharArray()) { // user 'reverse' to operate on reversed string
switch (c) {
case 'A' : sb.append('T'); break;
case 'T' : sb.append('A'); break;
case 'G' : sb.append('C'); break;
case 'C' : sb.append('G'); break;
default : sb.append(""); break; // handle you're exceptions here
}
}
System.out.println("x: " + sb);
System.out.println("Here is the reversed sequence: ");
System.out.println(reverse);
read.close();
}}
Well, switch-case is a kind of mapping technique which will map your case (as key) with it's values. In this case:
I am replacing 'A' with 'T' where the string contains 'A' by appending into the StringBuilder (to create a new string) and then break; which is a mandatory statement for single time execution only.
And the default keyword is for default case, which means if all of the cases are unsatisfied to be executed then the default case is called, you can do whatever you want to do by default if no case, condition matched.
Well, for your last question, You can make it generic if the problem states some pattern; if not you, unfortunately have to do it manually.
Use the replace method, but change your values to a "temporary" character. https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#replace(char,%20char)
Replace T -> x
Replace A -> T
Replace x -> A
Repeat for all your pairs.
Related
The following Java program is supposed to manipulate a string input by the user in such a way that the user will decide which character needs to be replaced with another and just the last character from the string should be replaced. Example if the user enters the string "OYOVESTER" and decides to replace "O" with "L", the program should output the following result: "OYLVESTER" (notice that only the last "O" was replaced with "L")
NOTE: YOU CANNOT USE BREAK COMMAND TO STOP THE LOOP. IT IS PROHIBITED.
import java.util.Scanner;
public class StringFun {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the string to be manipulated");
String inString = keyboard.nextLine();
String outString = "";
//Replace Last
System.out.println("Enter the character to replace");
char oldCharF = keyboard.next().charAt(0);
System.out.println("Enter the new character");
char newCharF = keyboard.next().charAt(0);
int count = 0; // variable that tracks number of letter occurrences
for(int index = inString.length() - 1;index >= 0;index--) {
if(inString.charAt(index) == oldCharF && count < 1){
outString = newCharF + outString;
outString = outString + inString.substring(0,index);
count++;
}
if (count < 1) {
outString = outString + inString.charAt(index);
}
}
System.out.print("The new sentence is: "+outString);
}
}
I keep getting the following output which is incorrect:
Enter the string to be manipulated
OYOVESTER
Enter the character to replace
O
Enter the new character
L
The new sentence is: LRETSEVOY
There are many simpler ways to achieve your requirement but I hope you have to demonstrate this with loops (without breaks)
Then you can use some thing like this :
boolean skip = false;
for (int index = inString.length() - 1; index >= 0; index--) {
if (!skip && inString.charAt(index) == oldCharF) {
outString = newCharF + outString;
skip = true;
}
else {
outString = inString.charAt(index) + outString;
}
}
PS : Using String concatenation inside loops is not recommended since
every String concatenation copies the whole String, usually it is preferable to
replace it with explicit calls to StringBuilder.append() or StringBuffer.append()
No break command seems like a weird condition. You could just a boolean value, and other methods, to break the loop when you need. Why not do something like this?
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the string to be manipulated");
String word = keyboard.nextLine();
//Replace Last
System.out.println("Enter the character to replace");
char oldCharF = keyboard.next().charAt(0);
System.out.println("Enter the new character");
char newCharF = keyboard.next().charAt(0);
int index = word.lastIndexOf(oldCharF);
if(index > 1){
word = word.substring(0,index) + newCharF + word.substring(index+1);
}
System.out.println("The new sentence is: " + word);
}
Being fairly new to Java, I have an exercise where the user will be asked to enter a word. Next, they will be asked to enter a number. Then the program will modify the word by taking the number and implementing it to change the string. For example, if the word "Hello" was entered, and the integer entered was the number "3", it will take each character in the string (Hello) and move them each 3 letters down in the alphabet, which would then make the output word "Khoor". I recently learned about method replacing (.replace) in the same chapter as this question but it seems like having to clarify every single letter with a replace would be too lengthy. This is what I have so far.
public class Lab03Exercise7 {
public static void main(String [] args)
{
// Prompt user to enter a string
System.out.print("Enter a word");
// Import Java scanner
Scanner input = new Scanner( System.in );
int numberinput;
String wordinput = input.nextLine();
// Prompt user to enter an integer
System.out.print( "Enter a number");
numberinput = input.nextInt();
}
}
You can do it as follows:
import java.io.IOException;
import java.util.Scanner;
public class Main {
public static void main(String[] args) throws IOException {
Scanner input = new Scanner(System.in);
System.out.print("Enter a word: ");
String wordInput = input.nextLine();
System.out.print("Enter a number: ");
int numberInput = input.nextInt();
StringBuilder updatedStr = new StringBuilder();
for (char c : wordInput.toCharArray()) {
updatedStr.append((char) (c + numberInput));
}
System.out.println("Updated string: " + updatedStr);
}
}
Explanation: Break the word into an array of characters and iterate through the array. During iteration, add the number to the character and append the updated character to a StringBuilder object. Note that you can add an integer to a char value but you need to cast it before appending to the StringBuilder object.
You can use something like this:
final StringBuilder sb = new StringBuilder();
for(int i = 0 ; i < wordinput.length(); i++) {
final char currentChar = wordinput.charAt(i);
sb.append((char)(currentChar + numberinput));
}
System.out.println(sb.toString());
So basically, we're going character by character and adding the shift that you've got from the user. here I don't handle the edge cases - where we need to rotate after z / Z
In general, this algorithm called Caesar Cipher and you can get some more info about it here: https://www.geeksforgeeks.org/caesar-cipher-in-cryptography/
As highlighted by #maio290' comment you have to use the ascii table to solve your problem, differentiating between lowercase characters and uppercase characters. Starting from the assumption we have a 26 chars alphabet (a-z and A-Z) in the example we are translating the chars of three positions so we will have for example:
"Hello" will be translated to "Khoor"
"zed" will be translated to "chg"
In the case of z char it will be translated to c, I'm posting an example explaining the situation:
public class Caesar {
public static String encode(String original, int k) {
char[] arr = original.toCharArray();
StringBuilder encoded = new StringBuilder();
for (char ch : arr) {
char initialCharacter = Character.isLowerCase(ch) ? 'a' : 'A';
int dec = ((int)(ch - initialCharacter) + k) % 26;
encoded.append((char)(dec + initialCharacter));
}
return encoded.toString();
}
public static void main(String[] args) {
System.out.println(encode("Hello", 3)); //<-- will print Khoor
System.out.println(encode("zed", 3)); //<-- will print chg
}
}
You have to transform your char to int and after retransform it to char , differentiating between lowercase chars and uppercase chars and assuming an alphabet of 26 chars , for further details see the ascii table.
I believe this is gonna help to solve your problem. Just do not forget to handle it after 122(letter z). You can check the ASCII table here (https://theasciicode.com.ar/)
public static void main(String[] args) throws Exception {
String word = "word";
char[] arr = word.toCharArray();
int count=0;
for (char c : arr) {
//!!Handle if the sum is bigger than 122 (letter z), you need to do some easy math.
arr[count] = (char) (((int)c) + 3);
count++;
}
String newWord = new String(arr);
}
I'm trying to make a short program that converts any string into T H I S F O N T.
For example: "This is a test sentence" turns into "T H I S I S A T E S T S E N T N C E"
I have a StringBuilder inside a while loop, but using finale.insert(i, '\t'); doesn't work.
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
while(i > finale.length()) {
if(finale.substring(i, i) == " ") {
i += 2;
finale.insert(i, '\t');
}
}
System.out.println(finale);
}
}
Any help?
You have a few issues with your code. Before I present an implementation that works, let's look at those other issues.
Your while loop checks if i > finale.length(). Since i = 0 the while loop never has a chance to begin.
You are comparing strings using == and this is not correct. == is used to confirm two objects are equal, not the value of two strings. You would need to use string.equals() instead.
You're doing too much in your loop anyway. Using a simple for loop can accomplish the goal quite simply.
Here is a new loop you can use instead of what you have:
for (int i = 1; i < finale.length(); i++) {
finale.insert(i++, " ");
}
The output: T H I S F O N T
For those unfamiliar with for loops, here's a very simple breakdown of how the above is structured.
The for loop is defined in three parts:
for (variable_to_increment; repeat_until_this_condition_is_met; modify_variable_on_each_iteration) {
// Code to be executed during each pass of the loop
}
First, we define a variable that we can track on each loop: int i = 1. By setting i = 1, we are going to skip the first character in the string.
The next statement, i < finale.length() means that we want to keep repeating this loop until we reach the length of our string. For example, if the string is 5 characters long and we've run the loop 4 times, i now equals 5 and is no longer less than the string's length, so the loop ends.
The last part is i++. This tells Java what we want to do with i after each loop. In this case, we want to increment the value by 1 each time the loop repeats.
Everything inside the brackets is, obviously, the code we want to execute on each loop.
You're saying while i>finale.length() but i is initialized as 0. You never enter the while loop.
Some issues with your code (see inline comments):
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
while(i > finale.length()) { // this condition is incorrect. Initially
// this condition will always be false
// if you input some sentence. It should be
// i < finale.length()
if(finale.substring(i, i) == " ") { // here preferably you should use
// equals method to compare strings
i += 2;
// you are only incrementing the i if the ith
// substring equals " ". Firstly, substring(i,i)
// will return empty string because the second argument
// is exclusive
finale.insert(i, '\t');
}
}
System.out.println(finale);
}
}
If you want to have an alternate method (not very optimal) for doing what you want to do, you can try the following approach:
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
String finale = x.toUpperCase().replaceAll(" ","").replaceAll("", " ");
System.out.println(finale);
}
}
First, convert the string to uppercase --> then remove all spaces between the words --> then insert spaces between all letters. The code line which does this is,
String finale = x.toUpperCase().replaceAll(" ","").replaceAll("", " ");
Here is a sample run:
Input text here: This is a sentence
T H I S I S A S E N T E N C E
The correct way with your method would be, just increment until you have twice the size of the initial String
while (i < x.length() * 2) {
finale.insert(i, '\t');
i += 2;
}
An easier way would be with a classic for-loop:
StringBuilder finale = new StringBuilder();
for (char c : x.toUpperCase().toCharArray()) {
finale.append(c).append('\t');
}
Use a for loop since you know the number of iterations:
Scanner input = new Scanner(System.in);
String x;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
int len = finale.length();
for (int i = 1; i < 2 * len; i+=2 ) {
finale.insert(i, '\t');
}
System.out.println(finale);
You are comparing strings with ==. Never do that; use equals instead.
For future readers: this job can be done elegantly using Java 8 Streams:
String result = str.chars()
.filter(i -> i != ' ')
.mapToObj(t -> (char) t)
.map(Character::toUpperCase)
.map(Character::valueOf)
.collect(Collectors.joining(" ");
The Captain Crunch decoder ring works by taking each letter in a string and adding 13 to it. For example, 'a' becomes 'n' and 'b' becomes 'o'. The letters "wrap around" at the end, so 'z' becomes 'm'.
This is what I've got after editing it a bit from peoples comments, but now it keeps telling me that output may have not been initialized and I have no clue why... also is there anything else I need to fix in my program?
In this case, I am only concerned with encoding lowercase characters
import java.util.Scanner;
public class captainCrunch {
public static void main (String[] Args) {
Scanner sc= new Scanner(System.in);
String input;
System.out.print("getting input");
System.out.println("please enter word: ");
input= sc.next();
System.out.print(" ");
System.out.print("posting output");
System.out.print("encoding" + input + " results in: " + encode(input));
}//end of main
public static String encode(String input){
System.out.print(input.length());
int length= input.length();
int index;
String output;
char c;
String temp= " ";
for (index = 0; index < length; index++) {
c = input.charAt(index);
if (c >= 'a' && c <= 'm') c += 13;
else if (c >= 'n' && c <= 'z') c -= 13;
output= temp + (char)(c);
}
return output;
}
}
It's called ROT13 encoding.
http://en.wikipedia.org/wiki/ROT13
To fix your algorithm you just need:
public static String encodeString (String input) {
StringBuilder output = new StringBuilder();
for (int i=0;i<input.length;i++) {
char c = input.charAt(i)
output.append(c+13); // Note you will need your code to wrap the value around here
}
return output.toString();
}
I haven't implemented the "wrapping" since it depends on what case you need to support (upper or lower) etc. Essentially all you need to do though is look at the range of c and then either add or subtract 13 depending on where it is in the ASCII character set.
You don't have any loop iterating over the character of your string. You have to iterate other the string from 0 to string.length().
The output may have not been initialized:
String output = "";
If you don't put = "" then you have never initialized it (it's essentially random garbage, so the compiler won't let you do it).
I'm having trouble with my program. I need to enter only capital letters, R,B,W. Validate the correct input and then sort the string. Output should be sorted with R's first, B's second and W's third. I can only get the alphabetized output, not the needed output. I don't know what to do next.
System.out.print("Enter a string of capital letters made up of R, B, W: ");
Scanner s = new Scanner(System.in);
String letters;
for (letters = s.nextLine(); !letters.matches("[RBW]+"); letters = s.nextLine())
{
System.out.println("Invalid entry. Please enter the correct letters.");
}
System.out.println("Thank you");
char[] sort2 = letters.toCharArray();
Arrays.sort(sort2);
String sorted = new String(sort2);
System.out.println("Here are your letters sorted:" +sorted);
You could do something like this. Have three different StringBuilders and add each letter to them accordingly. Then concatenate them in the right order when its done looping through the letters.
StringBuilder r = new StringBuilder();
StringBuilder w = new StringBuilder();
StringBuilder b = new StringBuilder();
for (char c : letters.toCharArray()){
switch(c){
case 'R' : r.append(c); break;
case 'B' : b.append(c); break;
case 'W' : w.append(c); break;
}
}
String sorted = r.toString() + b.toString() + w.toString();
System.out.println("Here are your letters sorted:" + sorted);
Arrays.sort(char[]) uses natural ordering, so you'll get Bs then Rs then Ws.
If you want an other sort order you have to implement your own Comparator and use Arrays.sort(T[], Comparator). Therefore you have to convert it to an Object array.
Arrays.sort(sort2, new Comparator<Char>() {
public int compare(Char o1, Char o2) {
if (Char.valueOf("R").equals(o1)) {
if (Char.valueOf("R").equals(o2)) {
return 0;
} else {
return -1;
}
} else if (Char.valueOf("B").equals(o1)) {
....
}
});