I'm trying to create an encryption scheme that replaces the letters in a String
with a corresponding letter.
For example, in the string "apple", the "a" is replaced with "k", and so on. Each letter has a fixed corresponding letter.
I want to get user input and store it into an array. Then I want to loop through the array and find each index of the String
. Then replace each index with the corresponding letter.
Here's what I cooked up so far but I'm unable to make the code run. I'm mainly getting, error: incompatible types
.
I can't determine whether I should be using the charAt
method and changing my variable types to char.
import java.util.*;
public class Encrypt {
public static void main(String [] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter the String Name to encrypt:");
String inputString = input.nextLine();
String[] str = new String[inputString];
replaceString();
}
public static void replaceString() {
for(int i = 0; i < str.length(); i++) {
if(str.indexOf(i) == "a") {
str.indexOf(i) = "k";
} else if(str.indexOf(i) == "b") {
str.indexOf(i) = "n";
}
//and so on A-Z...
System.out.print(str);
}
}
}
Why do you want to use String[]
? IMO you should use char[]
and the following code will do what you want:
public static void main(String[] args) throws IOException {
Scanner input = new Scanner(System.in);
System.out.println("Enter the String Name to encrypt:");
String inputString = input.nextLine();
char[] str = inputString.toCharArray();
replaceString(str);
}
public static void replaceString(char[] str) {
int length = str.length;
for(int i = 0; i < length; i++) {
if(str[i] == 'a') {
str[i] = 'k';
} else if(str[i] == 'b') {
str[i] = 'n';
}
}
System.out.println(Arrays.toString(str));
System.out.println(String.valueOf(str));
}
Running the program:
Enter the String Name to encrypt: bat
[n, k, t] nkt
You're looking for String#replace(char oldChar, char newChar)
Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
Your code would have to loop a pre-determined amount of times and store each String
in the array
Scanner input = new Scanner(System.in);
String[] str = new String[5];
for (int i = 0; i < 5; i++){
System.out.println("Enter the String Name to encrypt:");
String inputString = input.nextLine();
str[i] = inputString.replace('a', 'k');
}
for (String s : str){
System.out.println("Encrypted word: " + s);
}
Your previous way of declaring an array,
String[] str = new String[inputString];
is incorrect. Look here to practice more with arrays. Essentially, the formula is:
Type[] myArr = new Type[sizeOfArray];
Problem is String.indexOf()
gives you index of first occurence. It won't replace the string.
str.indexOf(i) = "k"; //won't replace anything here
BTW, there are several other syntax errors in your code.
Try this example, if you want use loops:
import java.util.Scanner; class Ideone { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the String Name to encrypt:"); String str = input.nextLine(); input.close(); str = replaceString(str); // note, self assignment System.out.println(str); } public static String replaceString(String str) { char[] tmp = str.toCharArray();// get all into array for (int i = 0; tmp.length > i; i++) { if ('a' == tmp[i]) { tmp[i] = 'k'; } else if ('b' == tmp[i]) { tmp[i] = 'n'; } } return new String(tmp); //create new string with modified array } }
Run code here
As suggested by others, you may also look into String.replaceAll()
:
import java.util.Scanner; class Ideone { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the String Name to encrypt:"); String str = input.nextLine(); input.close(); str = replaceString(str); System.out.println(str); } public static String replaceString(String str) { return str.replaceAll("a", "k").replaceAll("b", "n"); } }
Run code here
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