If I have two class constants:
List<String> workingList= new ArrayList<String>();
StringBuilder holder = new StringBuilder(50);
both residing within, call it class StringParser and primary method readStuff()...
public class StringParser{
public void readStuff(){
//parsing logic and adding <String> elements to
//said workingList...
}//end of method readStuff
followed by a method where I inspect the contents of workingList...
public String someReaderMethod()
{
int ind = 0;
for(int i = 0; i < workingList.size();i++)
{
if(workingList.get(i).contains(someExp))
{
workingList.remove(ind);
holder.append(workingList.get(i).toString());
}
else
{
++ind;
}
}
return holder.toString();
}
...given that StringBuilder holder now contains what workingList has removed, is there a way I can 'pass' the contents of StringBuilder to a new ArrayList?
Is there a reason why you want to use a StringBuilder? You can directly insert the values into a new ArrayList. I think you could do it in a simpler way.
List<String> discardedList = new ArrayList<String>();
public void readStuff() {}
public static List<String> someReaderMethod()
{
for(int i = 0; i < workingList.size(); i++)
{
if(workingList.get(i).contains(someExp))
{
discardedList.add(workingList.get(i));
workingList.remove(i);
}
}
return discardedList;
}
You will need a deliminator to parse string and then you can use Split method and convert String[] to ArrayList.
holder.append(tempList.get(i));
holder.append(";");//Deliminator
Now when you have to use it you need to do
String[] strings =holderString.split(";");
List<String> list = Arrays.asList(strings);
While appending your List elements to your StringBuilder object, you need to append an extra delimiter after every append..
Later on, you can split the String in StringBuilder on that delimiter, and then convert your String array thus obtained to an ArrayList..
Related
if(CoverageNames.size()>0) {
StringBuffer tmp = new StringBuffer();
for(int i =0; i<CoverageNames.size();i++) {
tmp.append(CoverageNames.get(i).getText());
tmp.append(";");
}
List<String[]> covNamesListReport= new ArrayList<>();
String[] CoverageNamesListReport={"CoverageNamesListReport",tmp.toString()};
covNamesListReport.add(CoverageNamesListReport);
String CovName= covNamesListReport.toString();
CoverageReportList("CoverageNames", CovName);
}
Coverage Report List is a method that accepts two string arguments.
I'm learning right now so any other approaches are also welcome.
When converting List<String[]> to string in line covNamesListReport.toString();, the contents of the inner arrays is NOT displayed as expected and look like [[Ljava.lang.String;#726f3b58] because the arrays' toString method is invoked.
To display the contents of the inner strings properly, nested List<String> could be used:
List<List<String>> covNamesListReport = new ArrayList<>();
List<String> CoverageNamesListReport = Arrays.asList("CoverageNamesListReport", tmp.toString());
covNamesListReport.add(CoverageNamesListReport);
String CovName = covNamesListReport.toString();
// -> [[CoverageNamesListReport, AAA;BB;CCC;]]
or Arrays.toString could be used just to convert a nested array:
List<String> covNamesListReport= new ArrayList<>();
String CoverageNamesListReport= Arrays.toString(new String[] {
"CoverageNamesListReport", tmp.toString()
});
covNamesListReport.add(CoverageNamesListReport);
String CovName= covNamesListReport.toString();
// -> [[CoverageNamesListReport, AAA;BB;CCC;]]
My return for the input "no" is showing up as "noon"
I'm seeing where it is adding the original word to the StringBuilder. How do I get it to not do that, and only add the characters to an empty StringBuilder, in reverse?
public class Palindrome
{
public static String reversed(String originalWord)
{
int lengthOfWord = originalWord.length();
StringBuilder reversedWordBuilder = new StringBuilder(originalWord);
for (int currentChar = lengthOfWord-1; currentChar >= 0; currentChar--)
{
reversedWordBuilder.append(Character.toString(originalWord.charAt(currentChar)));
}
return reversedWordBuilder.toString();
}
}
You are initializing the StringBuilder with the originalWord itself:
StringBuilder reversedWordBuilder = new StringBuilder(originalWord);
so it already have initial a value of "no", then you append the reversed one to it. You should initialize it with empty constructor like:
StringBuilder reversedWordBuilder = new StringBuilder();
and then to do your logic in the loop.
Since you already use StringBuilder you can do in one liner as it follows:
public static String reversed(String originalWord) {
return new StringBuilder(originalWord).reverse().toString();
}
I am working on the first part of a String permutation problem and I am just looping over the first char of a string and swap it with every following char of that same String. I initialized an empty ArrayList to store all of those permutations called listeFinale. When I am printing that ArrayList, I am getting a collection of object and not values ([[C#61bbe9ba, [C#61bbe9ba, [C#61bbe9ba, [C#61bbe9ba]), how can I print each char stored in the ArrayList?
import java.util.ArrayList;
import java.util.List;
public class checkPermu {
public static void main(String[] args) {
String myString = "aabc";
applyPermu(myString);
}
public static void applyPermu(String toCheck){
char[] newString = toCheck.toCharArray();
List listeFinale = new ArrayList();
for(int i = 0 ; i < newString.length ; i ++){
char temp = newString[0];
newString[0] = newString[i];
newString[i] = temp;
listeFinale.add(newString);
System.out.println(listeFinale);
}
}
}
First of all, don't use raw types for your List please.. Change:
List listeFinale = new ArrayList();
to:
List<char[]> listeFinale = new ArrayList<>();
As for your actual problem. Those values you see are the default toString() outputs of your inner character-arrays. You could iterate over your list, and call the java.util.Arrays.toString(char[]) method for them like this:
listeFinale.forEach(arr -> System.out.println(Arrays.toString(arr)));
Or, if you want to print them back as String again, use new String(char[]):
listeFinale.forEach(arr -> System.out.println(new String(arr)));
Try it online.
I have a series of String[] arrays which are list of words. Something like:
String[] ListOne = new String[100];
String[] ListTwo = new String[100];
/*And so on with other lists */
ListOne[0] = "word00";
ListOne[1] = "word01";
/*And so on till*/
ListLast[99] = "word 99 from last list";
Now I want a function for each list that, given a number returns the corresponding element (word):
public String GetFromListOne(int key) { return ListOne[key];}
Is there a way to avoid manually writing each of this getter functions?
In PHP, for example, I would just use the magic method __call,
or pass as an argument with the list name and reference it dynamically.
Is there a way to do something similar in Java?
Or an alternative strategy to achieve the same result?
You should look into inheritance.
What you basically must do is define an interface (or extend a List class)
public interface ListTest{
//**Gets keys from lists*//
GetFromListOne(int key);
}
then
public class Listone implements ListTest{
/** methods **//
GetFromListOne(int key);
/** methods **//
}
Have fun extending
http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html
You could use a 2 dimensional array, or a list of arrays and have your function take 2 parameters. One for the array that you want and the other for the element in the array.
2 dimensional array:
String[][] ListN = new String[100,100];
String getFromList(int n, int key) {
return ListN[n][key];
}
Or list of arrays:
List<String[]> listOfArrays = new ArrayList<String[]>();
listOfArrays.add(new String[100]);
listOfArrays.add(new String[100]);
String getFromList(int n, int key) {
return listOfArrays.get(n)[key];
}
Could you have a function that takes as input the key and the list number:
public String GetFromListOne(int list, int key) {
switch(list):
case 1:
return ListOne[key];
break;
case 2:
return ListTwo[key];
break;
...
}
or even better make an array of arrays:
String[][] ListOfLists = new String[10];
ListOfLists[0] = new String[100];
...
public String GetFromList(int list, int key) {
return ListOfLists[list][key];
}
Otherwise I don't know of a function to override like __call
String[] ListFour=new String[100];
String[] ListTwentyThree=new String[100];
String[] ListNine=new String[100];
String[] ListOne=new String[100];
Hashtable<Integer,String[]> yourlist=new Hashtable<Integer,String[]>();
yourlist.put(4, ListFour);
yourlist.put(23, ListTwentyThree);
yourlist.put(9, ListNine);
yourlist.put(1, ListOne);
System.out.println(yourlist.get(4)[5]);//fifth string in ListFour
System.out.println(yourlist.get(23)[51]);//fifty first string in List23
System.out.println(yourlist.get(9)[1]);//first stringin ListNine
another version:
Hashtable<Object,String[]> yourlist=new Hashtable<Object,String[]>();
yourlist.put("two multiplied by two", ListFour);
yourlist.put(23, ListTwentyThree);
yourlist.put(0.03, ListNine);
yourlist.put(true, ListOne);
System.out.println(yourlist.get("two multiplied by two")[5]);//fifth string in ListFour
System.out.println(yourlist.get(23)[51]);//fifty first string in List23
System.out.println(yourlist.get(true)[1]);//first stringin ListNine
Based in the __call PHP method, you can achieve this implementing a method that receives the list and the index, and using generics you can get something like this.
public class Utility {
public <T> T getElementFromArray(T[] array, int index) {
if (index >= array.length || index < 0) return null;
return array[index];
}
}
The pitfall of this method is that can't be used for primitive array holders, like int[]. The solution for these cases would be using the wrapper classes for primitive types.
public static void main(String[] args) {
Utility u = new Utility();
String[] ss = new String[2];
ss[0] = "Hello";
ss[1] = "world!";
System.out.println(u.getElementFromArray(ss, 0));
System.out.println(u.getElementFromArray(ss, 1));
int[] ii = new int[2];
ii[0] = 5;
System.out.println(u.getElementFromArray(ii, 0)); //compile error
//Solution: use wrapper classes
Integer[] ii2 = new Integer[2];
ii2[0] = 5;
System.out.println(u.getElementFromArray(ii2, 0));
}
Try this code
List<String[]> lists = new ArrayList<String[]>();
public String getFromLists(int key) {
List<String> res = new ArrayList<String>();
for (String[] s: lists){
res.add(s[key]);
}
return res.get(key);
}
or better
public String getFromLists(int key) {
return lists.get(key)[key];
}
I would like to pass a string array as a parameter to a function. Please look at the code below
String[] stringArray = {'a', 'b', 'c', 'd', 'e'};
functionFoo(stringArray);
Instead of:
functionFoo('a', 'b', 'c', 'd', 'e');
but if I do this I am getting an error stating that convert String[] into String. I would like to know if it is possible to pass the values like that or what is the correct way to do it.
How about:
public class test {
public static void someFunction(String[] strArray) {
// do something
}
public static void main(String[] args) {
String[] strArray = new String[]{"Foo","Bar","Baz"};
someFunction(strArray);
}
}
All the answers above are correct. But just note that you'll be passing the reference to the string array when you pass like this. If you make any modifications to the array in your called function, it will be reflected in the calling function also.
There is another concept called variable arguments in Java which you can look into. It basically works like this. Eg:-
String concat (String ... strings)
{
StringBuilder sb = new StringBuilder ();
for (int i = 0; i < strings.length; i++)
sb.append (strings [i]);
return sb.toString ();
}
Here we can call the function like concat(a,b,c,d) or any number of params you want.
More Info: http://today.java.net/pub/a/today/2004/04/19/varargs.html
I believe this should be the way this is done...
public static void function(String [] array){
...
}
And the calling will be done like...
public void test(){
String[] stringArray = {"a","b","c","d","e","f","g","h","t","k","k","k","l","k"};
function(stringArray);
}
look at familiar main method which takes string array as param
More than likely your method declaration is incorrect. Make sure the methods parameter is of type String array (String[]) and not simply String and that you use double quotes around your strings in the array declaration.
private String[] stringArray = {"a","b","c","d","e","f","g","h","t","k","k","k"};
public void myMethod(String[] myArray) {}
Feel free to use this how ever you like.
/*
* The extendStrArray() method will takes a number "n" and
* a String Array "strArray" and will return a new array
* containing 'n' new positions. This new returned array
* can then be assigned to a new array, or the existing
* one to "extend" it, it contain the old value in the
* new array with the addition n empty positions.
*/
private String[] extendStrArray(int n, String[] strArray){
String[] old_str_array = strArray;
String[] new_str_array = new String[(old_str_array.length + n)];
for(int i = 0; i < old_str_array.length; i++ ){
new_str_array[i] = old_str_array[i];
}//end for loop
return new_str_array;
}//end extendStrArray()
Basically I would use it like this:
String[] students = {"Tom", "Jeff", "Ashley", "Mary"};
// 4 new students enter the class so we need to extend the string array
students = extendStrArray(4, students); //this will effectively add 4 new empty positions to the "students" array.
I think you forget to register the parameter as String[]
please check the below code for more details
package FirstTestNgPackage;
import java.util.ArrayList;
import java.util.Arrays;
public class testingclass {
public static void main(String[] args) throws InterruptedException {
// TODO Auto-generated method stub
System.out.println("Hello");
int size = 7;
String myArray[] = new String[size];
System.out.println("Enter elements of the array (Strings) :: ");
for(int i=0; i<size; i++)
{
myArray[i] = "testing"+i;
}
System.out.println(Arrays.toString(myArray));
ArrayList<String> myList = new ArrayList<String>(Arrays.asList(myArray));
System.out.println("Enter the element that is to be added:");
myArray = myList.toArray(myArray);
someFunction(myArray);
}
public static void someFunction(String[] strArray)
{
System.out.println("in function");
System.out.println("in function length"+strArray.length );
System.out.println(Arrays.toString(strArray));
}
}
just copy it and past... your code.. it will work.. and then you understand how to pass string array as a parameter ...
Thank you