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How to pull numbers from an array

I currently have java homework that I would appreciate some help with. We are to calculate a team record scenario.
We are given the following numbers:
Team1 Points
{23,45,65,20}
Opponent Points
{20,30,20,18}
I threw these into an array. I also created a public boolean. Basically, you are to pull these points from the array to the boolean? And let the boolean decide which team won? Obviously team1 has won, but we are supposed to let the computer decide, not the human.
Here is my code:
public class TeamScore {
public static boolean Winner(int team1Points, int opponentPoints) {
if (team1Points > opponentPoints) {
return true;
} else {
return false;
}
}
public static void main(String[] args) {
// Scanner in = new Scanner(System.in);
int[] team1Points = { 23, 45, 65, 20 };
int[] opponentPoints = { 20, 30, 20, 18 };
int team1 = 1;
int opponent = 1;
for (int i = 0; i < 5; i++) {
if (Winner(team1Points[i], opponentPoints[1])) {
team1 += 1;
} else {
opponent += 1;
}
}
for (int i = 0; i < 5; i++) {
if (team1 > 0 && opponent == 0) {
System.out.println("Team 1 has the perfect record!");
} else {
System.out.println("Win" + Arrays.toString(team1Points));
System.out.println("Loss" + Arrays.toString(opponentPoints));
}
}
}
Could anyone possibly help me? I am currently in programming II, but I did not have the best teacher in programming I. Any help would be appreciated!
EDIT:
I do not think this is a duplicate question because I already can fix it by changing the variable i-->1. My problem is that the computer thinks that team1 has already won regardless of the score.
When I run the code I am getting an java.lang.ArrayIndexOutOfBoundsException error. However when I change team1Points[i] to team1Points[1] then it goes okay and tells me that "Team 1 has the perfect record!". However, if I change some of the array values for team1Points to be less than opponentPoints then it still says "Team 1 has the perfect record!".

Not sure why you have a method Winner (also as Kevin said, it should be winner because of naming conventions) which turns ´(a > b)´ into a large if-statement. Similar stuff appear elsewhere in your code.
Your variables ´team1, opponent = 1´ inexplicably start with the value 1, am I to understand this as a way for your code to imply to a reader that both teams initialize at a win? Using 0 would probably make more sense.
Your game ought to crash from an indexoutofboundsexception at ´team1Points[i]´, as you have arrays of length 4, but your loops runs 5 times (the currently used range is [0-4], inclusive). Changing your loops to i=1 won't help, as the issue is that you eventually encounter team1Points[4] due to the i < 5 statement.
I don't know what game you are modelling or how it works, but the comparison ´Winner(team1Points[i],opponentPoints[1])´ looks like a blatant error to me (you always look at the opponents score for their second round).
Why are you printing your results 5 times? If you want to print the first message only when team1 won all rounds and the point for each round otherwise, you would need to use the loops counter as an index to the arrays in second case. First case should break loop so its not written five times, in addition you don't need to check team1>0 && opponent==0 as it's enough to only check if ´opponent==0´ (speaking of this conditional, it only works if you initialize the variables at 0 as I mentioned before). You could have checked if team1 equals size of the array instead, but imo thats more of a hassle than opponent==0.
Lastly, please fix your indenting. use the preview system so you can make double sure before posting.
Edit: Kevin also brings up a good point that you should be using the length of the array in your loops second statement.

The below code wont execute with some inputs

Sorry for such a basic level question guys. But I'm starter in programming. Not a computers guy. So kindly help me.
In this code when I give input 1000000000, 1000000000, 999999999 the answer should be 4. But my answer is 1. I expect the if statement to execute but it is not executing here.
if you take m*n as a room and "a" as the side as a square tile. Then I want to count MINIMUM no. of tiles required to fill the floor of room. tiles may cover a bit more area but should not leave the room empty. this is my objective. It's working with inputs like 6,6,4 or 15,20,13 etc.
Now its working guys. I had posted the correct code with those minor changes below.
import java.util.Scanner;
public class TheatreSquare {
private static Scanner input;
public static void main(String[] args) {
input = new Scanner(System.in);
float m=input.nextFloat();
float n=input.nextFloat();
float a=input.nextFloat();
long i=(int)(m/a);
long j=(int)(n/a);
if((a*a*i*j)<m*n){
if(a*i<m){
//to check weather it is entering if()
System.out.println("true");
i+=1;
}
if(a*j<n){
System.out.println("false");
//to check weather it is entering if()
j+=1;
}
}
System.out.println((double)(i*j));
}
}

Your floats are overflowing when you multiply them. Defining m, n and a as doubles will solve the issue:
double m = input.nextDouble();
double n = input.nextDouble();
double a = input.nextDouble();

The int conversion loses precision.
Here in this case, a*a*i*j is equal to m*n Hence the if loop will not execute. Also a*i is equal to m and a*j is equal to n.
Hence i isi and j is 1, so i*j is 1.
You need to allow it to go if it is equal too.
Replace
if((a*a*i*j)<m*n){
if(a*i<m){
//to check weather it is entering if()
System.out.println("true");
i+=1;
}
if(a*j<n){
System.out.println("false");
//to check weather it is entering if()
j+=1;
}
}
with
if((a*a*i*j) <= m*n){
System.out.println("Entered if block");
if(a*i <= m){
//to check weather it is entering if()
System.out.println("true");
i+=1;
}
if(a*j <= n ){
System.out.println("false");
//to check weather it is entering if()
j+=1;
}
System.out.println("i is:"+ i +"j is:"+j);
}

thankyou #Mureinik, #Uma Lakshmi Kanth, #Diego Martinoia for helping to solve this. All your answers contributed to solve my question. this is working now. as #Mureinik said my floats are overflowing( though I dont know the meaning). I used Double instead of float and that's it. its working. :-)
import java.util.Scanner;
public class TheatreSquare {
private static Scanner input;
public static void main(String[] args) {
input = new Scanner(System.in);
double m=input.nextDouble();
double n=input.nextDouble();
double a=input.nextDouble();
long i=(long)(m/a);
long j=(long)(n/a);
if((a*a*i*j) <m*n){
if(a*i < m){
//to check weather it is entering if()
i+=1;
}
if(a*j < n ){
//to check weather it is entering if()
j+=1;
}
}
System.out.println((long)(i*j));
}
}

The reason for your behavior is that you are reading numbers as floats. Floats have limited precision, so your m n and a are the same value (at runtime). Reading them as long (and getting rid of all the decimal stuff) should help. But, as mentioned in the comment, we don't know what you wanted to achieve!
--- EDIT DUE TO NEW INFO ---
You have to cover an area of m times n square meters. You have an unit of computation of 1 tile, i.e. a times a square meters (both assumed to be decimal).
Assuming you can cut your tile with good-enough precision, your result will be:
Math.ceiling((m*n) / (a*a));
i.e., either your area is an exact multiple of your tiles (and you can always cut them in rectangles to match the shape of the room), or you'll have some "spare" space to fill in, thus you will need 1 more tile, a part of which you'll use to cover the remaining space, and a part of which you'll throw away.

The correct Recursive backtracking algorithm?

My assignment is to find a way to display all possible ways of giving back change for a predetermined value, the values being scanned in from a txt file. This must be accomplished by Recursive Backtracking otherwise my solution will not be given credit. I will be honest in saying I am completely lost on how to code in the appropriate algorithm. All I know is that the algorithm works something like this:
start with empty sets.
add a dime to one set.
subtract '10' from my amount.
This is a negative number, so I discard that set: it is invalid.
add a nickel to another (empty) set.
subtract '5' from my amount.
This equals 2; so I'll have to keep working on this set.
Now I'm working with sets that already include one nickel.
add a dime to one set.
subtract '10' from my amount.
This is a negative number, so I discard that set: it is invalid.
repeat this with a nickel; I discard this possibility because (2 - 5) is also negative.
repeat this with a penny; this is valid but I still have 1 left.
repeat this whole process again with a starting set of one nickel and one penny,
again discarding a dime and nickel,
and finally adding a penny to reach an amount of 0: this is a valid set.
Now I go back to empty sets and repeat starting with a nickel, then pennies.
The issue is I haven't the slightest clue on how or where to begin, only that that has to be accomplished, or if any other solutions are apparent.
This is my code thus far:
UPDATED
import java.io.*;
import java.util.*;
import java.lang.*;
public class homework5 {
public static int penny = 1;
public static int nickle = 5;
public static int dime = 10;
public static int quarter = 25;
public static int halfDollar = 50;
public static int dollar = 100;
public static int change;
public static void main(String[] args) throws FileNotFoundException {
ArrayList<Integer> coinTypes = new ArrayList<Integer>();
Integer i;
File f = new File (args[0]);
Scanner input = new Scanner(f);
input.nextLine();
while(input.hasNextInt()) {
i = input.nextInt();
coinTypes.add(i);
}
change = coinTypes.get(coinTypes.size()-1);
coinTypes.remove(coinTypes.size()-1);
System.out.println("Found change"); //used for debugging
System.out.println("Change: " + change);
System.out.println(coinTypes);
}
boolean findChange(int change, List<Integer> coinTypes,
List<Integer> answerCoins) {
if(change == 0) {
return true;
}
if(change < 0) {
return false;
} else {
for(Integer coin : coinTypes) {
if(findChange(change - coin, coinTypes, answerCoins)){
answerCoins.add(coin);
return true;
}
}
List<Integer> answer = new ArrayList<Integer>();
boolean canFindChange = findChange(change, coinTypes, answer);
if(canFindChange) {
System.out.println(answer);
} else { System.out.println("No change found");
}
return false;
}
}
Here is the input file that I scan in
java homework5 hwk5sample1.txt
// Coins available in the USA, given in cents. Change for $1.43?
1 5 10 25 50 100
143
OUTPUT
Found change
Change: 143
[1, 5, 10, 25, 50, 100]
So using the numbers in my coinTypes ArrayList, I need a generic code algorithm to show all possible ways of receiving, for example, 143 ($1.43) back in change using the coins in the file with all pennies being the last way to show it.
Please do not think I want you to write me the algorithm, I am simply wanting help writing one otherwise I will learn nothing. Thank you all for any answers or help you can give it means a lot to me! Please let me know if i missed anything or you need more info

The example that you walk through seems to be mostly correct. The only error is this: again discarding a dime and nickel, which should be again discarding a *penny* and nickel (but I think that's just a typo.)
To write a recursive backtracking algorithm, it is useful to think of the recursive call as solving a subproblem of the original problem. In one possible implementation of the solution, the pseudocode looks like this:
/**
* findChange returns true if it is possible to make *change* cents of change
* using the coins in coinTypes. It adds the solution to answerCoins.
* If it's impossible to make this amount of change, then it returns false.
*/
boolean findChange(int change, List<Integer> coinTypes, List<Integer> answerCoins) {
if change is exactly 0: then we're done making change for 0 cents! return true
if change is negative: we cannot make change for negative cents; return false
otherwise, for each coin in coinTypes {
// we solve the subproblem of finding change for (change - coin) cents
// using the recursive call.
if we can findChange(change - coin, coinTypes, answerCoins) {
// then we have a solution to the subproblem of
// making (change - coins) cents of change, so:
- we add coin to answerCoins, the list of coins that we have used
- we return true // because this is a solution for the original problem
}
}
//if we get to the next line, then we can't find change for any of our subproblems
return false
}
We would call this method with:
List<Integer> answer = new ArrayList<Integer>();
boolean canFindChange = findChange(change, coinTypes, answer);
if(canFindChange) {
System.out.println(answer); // your desired output.
}
else {
System.out.println("Can't find change!");
}

Average of n numbers in java

Using loop I want to calculate the average of n numbers in Java and when user enters 0 the loop ends.
Here is the code that I have written:
public class start {
public static void main(String[] args) {
System.out.println("Enter an int value, the program exits if the input is 0");
Scanner input = new Scanner (System.in);
int h = 0;
while (input.nextInt() == 0){
int inp = input.nextInt();
int j = inp;
int i = 0;
h = j + i;
break;
}
System.out.println("The total is: "+ h);
}
}
Am I making any logical error?

Don't name the sum h, but sum.
The while-condition is wrong
Why do you use inp and j and i?
There is an unconditional break - why?
You talk about the average. Do you know what the average is?
Your output message is not about average - it is about the sum.

"Am I making any logical error?"
Yes. This looks like a homework problem so I won't spell it out for you, but think about what the value of i is, and what h = j + i means in this case.
You also need to be careful about calling input.nextInt(). What will happen when you call it twice each time through the loop (which is what you are doing)?

Homework, right?
Calling input.nextInt() in the while loop condition and also to fill in int inp means that each trip through the loop is reading two numbers (one of which is ignored). You need to figure out a way to only read one number per loop iteration and use it for both the == 0 comparison as well as for inp.
Additionally, you've done the right thing having h outside the while loop, but I think you're confusing yourself with j and i inside the loop. You might consider slightly more descriptive names--which will make your code much easier to reason about.

You need to keep a counter of how many numbers you read so you can divide the total by this number to get the average.

Edited the while loop:
while(true){
int e=input.nextInt();
if(e==0) break;
h+=e;
numberOfItems++;
}
Your original implementation called nextInt() twice, which has the effect of discarding every other number (which is definitely not what you intended to do).

Assuming that you asking the user only once, to enter and if the number if zero you simply want to display the average. you need a variable declared outside the while loop that will keep adding different numbers entered by the user, along with a second variable which track the number of cases entered by the user and keep incrementing itself by one till number is not zero as entered by the user. And as the user Enters 0, the loop will break and here our Average will be displayed.
import java.util.Scanner;
public class LoopAverage
{
public static void main(String[] args0)
{
Scanner scan = new Scanner(System.in);
System.out.println("Enter any Integer value : ");
int value = -1, sum = 0, count = 0;
while((value = scan.nextInt()) != 0)
{
count++;
sum = sum + value;
}
System.out.println("Average : " + (sum / count));
}
}
Hope that might help,
Regards

yes, oodles of logical errors.
your while loop condition is wrong, you're consuming the first value
you enter and unless that number is 0 you never enter the loop at all
i var has no purpose
you're breaking after one iteration
you're not calculating a running total
you're not incrementing a count for the average dividend
you're not calculating an average
This looks like you threw some code together and posted it. The most
glaring errors would have been found just by attempting to run it.
Some other things to consider:
Make sure to check for divide by 0
If you do an integer division, you might end up with an incorrect
average, as it will be rounded. Best to cast either the divisor or
dividend to a float
variable names should be helpful, get into the habit of using them

I recommend you to refer to the condition of "while" loop: if condition meets, what would the program do?
(If you know a little bit VB, what is the difference between do...until... and do...while...?)
Also, when you call scanner.nextInt(), what does the program do? For each input, how should you call it?
Last but not least, when should you use "break" or "continue"?
For the fundamentals, if you are in a course, recommend you to understand the notes. Or you can find some good books explaining details of Java. e.g. Thinking in Java
Enjoy learning Java.

Java boolean if question

I am making a lottery program where I am asking if basically they would like a quick pick ticket. The numbers for their ticket of course would be random since it is a quick pick but the first four numbers range from 0-9 while the fifth number only goes up to 0-4. I am trying to ask them to input a button such as either "1" for no or "2" for yes if they don't want one then it would skip this step. But I am doing the boolean part incorrectly though. Could someone help me out?
Here is an example
System.out.println("Do you want Quick pick, 1 for no or 2 for yes? The first four numbers is from a separate set of 0 to 9 and the fifth number is from a set of 0 to 4.");
QuickPick=keyboard.nextInt();
if((QuickPick==1)){
return false;
}
if((QuickPick==2)){
return true;
int n = (int)(Math.random()*9+0);
System.out.println("Your QuickPick numbers are: " + kickerNumbers + kickerPowerball);
}
I still haven't gotten around to making the line of code for the final number of 0-4, just the first four numbers, so I haven't forgotten that.

Your code for case 2 immediately does a return true; which ends the method (I assume this is in a method) right then and there. Your other lines don't get execute at all.
Consider using a switch() statement here, it'll make it easier to read:
switch(QuickPick)
{
case 1:
return false;
case 2:
int n = (int)(Math.random()*9+0); // Why is n here? You don't do anything with it?
System.out.println("Your QuickPick numbers are: " + kickerNumbers + kickerPowerball);
return true;
default:
// Uh oh - someone did something bad maybe just return false?
return false;
}
Also your code for case 2 is definitely wrong, you need to generate a total of five numbers, using bounds 0-9 for the first 4 and 0-4 for the last one. You'll want to use Java's Random to do this (not Math.Random) something like:
Random rand = new Random();
int somethingRandom = rand.nextInt(10);
// Will give you an integer value where 0 < val < 10
// You can call rand.nextInt as many times as you want
To avoid doing your homework for you -- I'll follow the typical CS textbook line and say "Implementation left as an exercise."

The code after return true will not be executed - you need to put that prior to the return statement

Like Marvo said, you dropped a brace in your if.
But you also have faulty logic. I'm not quite sure what the purpose of the method you're in is (that returns a boolean value). But your last few lines will never be reached unless the user types in something like 3 or 42.
Assuming the method is supposed to a) Ask if the user wants a Quick Pick b) Calculate the Quick Pick, if desired c) Return true/false depending on whether the Quick Pick happened or not, you should have:
public boolean doQuickPick()
{
System.out.println("Do you want Quick pick, 1 for no or 2 for yes? The first four numbers is from a separate set of 0 to 9 and the fifth number is from a set of 0 to 4.");
QuickPick=keyboard.nextInt();
if((QuickPick==1)){
return false;
}
if((QuickPick==2)){
int n = (int)(Math.random()*9+0);
System.out.println("Your QuickPick numbers are: " + kickerNumbers + kickerPowerball);
return true;
}
}
As a separate issue, it'd be much better style to break that into several methods. boolean yesNoPrompt(String message), generateQuickPick(), etc.
Your question is kind of unclear, so I'm afraid I can't be much more help than that. Do post any clarifications / further questions if you have them.

if((QuickPick==2)){
return true;
int n = (int)(Math.random()*9+0);
System.out.println("Your QuickPick numbers are: " + kickerNumbers + kickerPowerball);
}
In the above copied code from your question, I see that you will be getting compilation errors in your IDE. Your IDE will complain about "Unreachable Code" for the line that is just below the return statement. So, you need to put the return statement at the end of the if block.