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trying to print arrays in java [closed]

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I had a code I needed to submit and every time I try to run it, I get the same errors over and over again.
Here's the question
Write the following Java methods:
(a). readValues to input ten integer values into an array of integers
TAB from a text file “Values.txt”. This array TAB is passed to the
method as parameter. Assume that the number of students in the file is
equal to the length of the array.
(b). oddValues that takes the array TAB as parameter and returns the
number of odd values found in TAB.
(c). replaceOdd that takes the array TAB as a parameter. It should
replace every odd value in TAB by the sum of all odd values.
Hint: your method must first compute the sum of all odd values.
(d). printValues that takes the array TAB as a parameter and prints
its content on the screen.
(e). main that declares the array TAB and calls the above four
methods.
N.B.: In your program, use the methods and variable names as mentioned
above.
And this is the code:
import java.util.*;
import java.io.*;
public class Finalexam
{
public static void main (String [] args ) throws FileNotFoundException
{
int sum=0;
int [] TAB=new int [10];
ReadValues(TAB);
oddValues(TAB);
replaceOdd(TAB);
printValues(TAB);
System.out.println("The sum is" + sum);
}
public static void ReadValues (int [] TAB)
{
{ int i;
for(i=0; i<10; i++){
Scanner s = new Scanner ("Values.txt") ;
TAB[i]=s.nextInt();
}
}
s.close();
}
public static double oddValues(int[] TAB)
{
int i;
double odd=0;
int fn=0;
for(i=1; i<odd; i++){
while(odd % 2 !=0)
{
odd = fn;
}
break;
}
return fn;
}
public static int replaceOdd(int[] TAB)
{
int re=0;
for(int i=0; i<TAB.length; i++){
re = re/TAB.length;
}
return re;
}
public static void printValues(int[] TAB)
{
int i;
for(i=0; i<10; i++){
System.out.println(TAB[i]+"\t");
}
System.out.println();
}
}
In which part I'm doing wrong? I cant even run it.

Firstly there is a compilation error in your code.
In your method
public static void ReadValues (int [] TAB)
{
{ int i;
for(i=0; i<10; i++){
Scanner s = new Scanner ("Values.txt") ;
TAB[i]=s.nextInt();
}
}
s.close();
}
You have too many extra brackets, well thats not the problem though, the problem is the scanner object s is declared inside the for loop where as you are closing it later outside the loop, since the scope of the variable is not outside the loop, hence the error.
The correct way should be
public static void readValues (int [] tab){
int i;
Scanner s = new Scanner ("Values.txt") ;
for(i=0; i<10; i++){
tab[i]=s.nextInt();
}
s.close();
}
Also there are many thing that will work in your code but is a bad practice or is not following conventions.
Variable names (e.g tab) should always be in camel case. It should only be a capital if it is a constant, which is not in your case.
The method names starts with small letter.
Also you are calling the two methods replaceOdd(TAB) and oddValues(TAB) But the return value is not being used anywhere.
FileNotFoundException will never be thrown
If you closely look at this method below
public static double oddValues(int[] TAB) {
int i;
double odd = 0;
int fn = 0;
for (i = 1; i < odd; i++) {
while (odd % 2 != 0) {
odd = fn;
}
break;
}
return fn;
}
The loop will never execute as odd is 0 so i<odd will always be false. Also the logic for odd is wrong.
public static int replaceOdd(int[] TAB){
int re=0;
for(int i=0; i<TAB.length; i++){
re = re/TAB.length;
}
return re;
}
This method will always return zero, the logic is wrong.
There are many more logical errors. I would suggest you to look into them as well

Calling method from another class that's an array

I am calling a method from another class. The method contains an integer array. I am trying to stay away from inputting the index manually.
I am trying to search for numbers within a range.
example:
ArrayList: {1,5}, {5,10}, {10,15}
Input: enter 3
Process: search for number within range
output: 1,5
The driver class is storing the objects from the main class called Numbers into ArrayList. The main class have an accessor call getNumbers. getNumbers contains an integer array with 2 elements. The driver is calling getNumbers to validate the entry that users input.
The code below works but I'm told it's consider bad coding to code entering the indexes. I want to know how to output the array from getNumber method without knowing the array length of getNumber?
example of what I have:
for(int i = 0; i < example.size(); i++)
//number is the integer that is inputted.
if(example.get(i).getNumbers()[1] > number &&
example.get(i).getNumbers()[0] <= numbers)
System.out.println(example.get(i));
Should I add another for loop?
example of what I am thinking of:
for(int i = 0; i < example.size(); i++)
for(int j = 0; j < example.get(i).getNumbers.length; j++){
if(example.get(i).getNumbers()[j] > number &&
example.get(i).getNumbers()[j] <= numbers)
System.out.println(example.get(i));
}
}
Edit: Changed how I worded some things and fixed the code of what I think I should do.

The code below works but I'm told it's consider bad coding to code
entering the indexes. I want to know how to output the array from
getNumber method without knowing the array length of getNumber ?
If you don't want to do the validations with array indexes for your first element and second element in the array, then you can solve the problem by modifying your Numbers class as shown below:
(1) Define two int variable members (currently you have only one)
(2) Add a method isInLimits(int input) to validate the range
(3) Override toString() which can be used to print the object as String
Numbers class (modified):
public static class Numbers {
private int firstElement;
private int secondElement;
public int getFirstElement() {
return firstElement;
}
public void setFirstElement(int firstElement) {
this.firstElement = firstElement;
}
public int getSecondElement() {
return secondElement;
}
public void setSecondElement(int secondElement) {
this.secondElement = secondElement;
}
//checks the input is in the range of this object elements
public boolean isInLimits(int input) {
if(input >= firstElement && input < secondElement) {
return true;
} else {
return false;
}
}
#Override
public String toString() {
return "{"+firstElement+","+secondElement+"}";
}
}
Usage of Numbers Class:
public static void main(String[] args) {
int userInput = 10; //get it from user
List<Numbers> example = new ArrayList<>();
//Add Numbers objects to example list
for(int i=0;i< example.size();i++) {
Number numberTemp = example.get(i);
//call Numbers object's isInLimits
if(numberTemp.isInLimits(userInput)) {
System.out.println(numberTemp);
}
}
}

how i can optimize this java code?

In below code string is passed in a method with numbers separated by space,
now we need to provide sum of smallest two numbers in the string.
public class SumNearZero {
public static int SumNearZero(String s) {
String temp=s;
int t1=0;
for (int i = 0; i <s.length(); i++) {
if(temp.contains(" "))
{
t1++;
temp=temp.substring(temp.indexOf(" ")+1);
}
}
int a[]=new int[++t1];
int index=0;
for(int i=0; i<s.length(); i++)
{
if(s.contains(" "))
{
a[index]=Integer.parseInt(s.substring(0,s.indexOf(" ")));
s=s.substring(s.indexOf(" ")+1);
index++;
}
}
a[index]=Integer.parseInt(s);
for (int i = 0; i < a.length; i++) {
for(int j=0; j<a.length-1; j++)
{
int c=a[j],n=a[j+1];
if(c>n)
{
int t=c;
a[j]=n;
a[j+1]=t;
} } }
int result=a.length>1 ? a[0]+a[1]:a[0];
return result;
}
public static void main(String[] args) {
System.out.println(SumNearZero("35 96 10 20 5"));
}
}
Above code is working fine but i want to reduce the code. if you provide some suggestion regarding this, I'll be happy to learn from you.
Restrictions : use of Collections, predefined methods e.g(String.split(),Arrays.sort()...)

I would suggest you not perform your calculation and display in a constructor, create a static method and invoke it. Next, in that method, create a List of Integer by iterating the substrings generated by splitting your input on one (or more) white space characters. Then, sort the List. Finally, return the sum of the first two elements1. It's also a good to do some error checking for one number (or no numbers). That might look something like
public static int sumNearZero(String s) {
List<Integer> al = new ArrayList<>();
for (String str : s.split("\\s+")) {
al.add(Integer.parseInt(str));
}
if (al.isEmpty()) {
return 0;
}
Collections.sort(al);
if (al.size() == 1) {
return al.get(0);
}
return (al.get(0) + al.get(1));
}
Then invoke it like
public static void main(String[] args) {
System.out.println(sumNearZero("35 96 10 20 5"));
}
I get (as I expected)
15
1once sorted the first two are the minimum, and the last two are the maximum

You can make it faster by using for each loop instead of for loop every time, it is more recommended and faster approach whenever loop is increasing for array, lists etc.
Plus more you can get all numbers in string by using split function which retrives you array of those numbers.and then you can put your logic for getting small numbers.this will reduce counting and increase speed highly in general if you want to learn about optimization then this is definitive guide i suggest you to go through it. and see this answer.

Looks like an exercise, so not giving actual code.
Use String.split and Arrays.sort

Object in ArrayList is changing

I made a test program because I am trying to get back into Java after working in PL/SQL. I created a class Numbers that contains an integer, a getter and a setter. I have another class Test that is creating an instance of Numbers, and also adds that instance to a List. I created a for loop that loops two times and sets the value of the integer in Numbers equal to i. I then add that instance of Numbers to the List numbersList. I then do a print screen of the value that was added to the List. I do a total of 3 prints, one print the first time through the loop that prints the first position in the List, then I print two times during the second time through the loop,the first position in the List again, and the second position in the List. I was expecting to get 0,0,1 as the result. I am getting instead 0,1,1 as the result and I cannot figure out why. I am not changing anything in the first position in the List (numbersList[0]) during the second time through the loop, all I am doing is adding an instance of Numbers into the second position in the list (numbersList[1]).
import java.util.ArrayList;
import java.util.List;
public class Tests {
static int x;
public static void main(String[] args) {
List<Numbers> numbersList = new ArrayList<Numbers>();
Numbers numbers = new Numbers();
Numbers numbers2 = new Numbers();
for (int i = 0; i < 2; i++) {
if (i == 0) {
numbers.setVariable(i);
numbersList.add(numbers);
System.out.println(numbersList.get(0).getVariable());
}
if (i > 0) {
numbers2.setVariable(i);
numbersList.add(numbers2);
System.out.println(numbersList.get(0).getVariable());
System.out.println(numbersList.get(1).getVariable());
}
}
}
}
public class Numbers {
public static int a = 5;
public static void setVariable(int b) {
a = b;
}
public static int getVariable() {
return a;
}
}

public static int a = 5 means that all instances of Numbers share the same variable because of the static keyword.
Therefore, when you do numbers2.setVariable(i);, the variable is also changed for numbers. Hence the 0,1,1
If you want instance variables remove the static keywords from Numbers.

Your class Numbers has no instance fields (everything is static, or class level).
It should look something like (and overriding toString() is a good idea),
public class Numbers {
public int a = 5;
public void setVariable(int b){
a = b;
}
public int getVariable(){
return a;
}
#Override
public String toString() {
return String.valueOf(a);
}
}
By overriding toString() you can more easily print instances of Numbers. For example,
System.out.println(numbersList);

Incorrect output while using methods in recursion. The return statement in a method returns an integer at the end of the output

package abcde;
public class Abcde{
public static void main(String[] args){
System.out.println(recursion(97));
}
public static int recursion (int n) {
for ( int i = n; i< 123; i++)
{
String achar = new Character((char)i).toString();
System.out.print(achar);
}
return -1;
}
}
The desired output has to be abcdefghijklmnopqrstuvwxyz while the output is abcdefghijklmnopqrstuvwxyz-1
I dont want the -1 at the end.
When i change the input type to void, the method does not work.
What can we do about it?

The final -1 gets printed outside the recursion method: main() prints what recursion returns, which happens to be -1.
If you change the return type of recursion to void, you need to call it as a method, not as an expression. In other words, you can no longer call println(recursion(97)) because println expects a value to print.
As a side note, in order to be recursive a method needs to have a code path that calls the same method, directly or indirectly. Since the "calling itself" feature is missing from your recursion method, consider renaming it to iteration.

rewrite it to:
public static void main(String[] args){
noRecursion(97);
}
public static void noRecursion (int n) {
//^^^^
for (int i = n; i< 123; i++) {
System.out.print((char)i);
}
}

Actually, your recursion function doesn't return anything but -1, but It does print all of the other characters before it returns.
if you change it to
public static void notRecursion (int n) {
for ( int i = n; i< 123; i++)
{
String achar = new Character((char)i).toString();
System.out.print(achar);
}
}
and then just call it from your main like
notRecursion(97);
It will print what you want it to print
Or
public static String recursion (int n)
{
if(n >97 +1)
{
System.out.print(recursion(n-1));
}
String achar = new Character((char)n).toString();
return(achar)
}
and then call it with
System.out.println(recursion(123));

Choose pure functions over side effects:
public static String iteration (int n) {
final StringBuilder b = new StringBuilder();
for (char c = (char)n; c < 123; c++)
b.append(c);
return b.toString();
}
Now you can call this method as you are calling it now, and print its result.