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Null pointer exception when referencing an object

I'm writing a dice roller program for a project, and it prints an error when I try to access the Calculations object. Everything else works, from what I can tell (the variables are set correctly, everything prints in order.
Calculations c;
int stage = 0;
int number;
int die;
int mod;
int modnum;
int inc = 0;
int[] num = new int[20];
boolean plusminus;
int spot = 0;
void setup() {
startScreen(inc);
}
void draw() {
}
//initial prompt screen
void startScreen(int stage) {
switch(stage) {
case 0:
println("How many dice? (up to 9)");
break;
case 1:
number = num[spot];
//noLoop();
println("Modifiers? (press + or -)");
break;
case 2:
mod = num[spot];
if (mod == 10) {
plusminus = true;
}
if (mod == 11) {
plusminus = false;
}
//noLoop();
println("how much?");
//loop();
break;
case 3:
modnum = num[spot];
//noLoop();
println("which dice? (1 = d2, 2 = d3, 3 = d4, 4 = d6, 5 = d8, 6 = d10, 7 = d12, 8 = d20, 9= d100");
break;
case 4:
die = num[spot];
c.finalcalc();
break;
}
}
void keyPressed() {
if (keyPressed) {
if (keyCode == ENTER) {
inc++;
loop();
startScreen(inc);
noLoop();
}
if (keyCode != ENTER) {
if (key == '1') {
num[spot] = 1;
println(num[spot]);
} else if (key == '2') {
num[spot] = 2;
println(num[spot]);
} else if (key == '3') {
num[spot] = 3;
println(num[spot]);
} else if (key == '4') {
num[spot] = 4;
println(num[spot]);
} else if (key == '5') {
num[spot] = 5;
println(num[spot]);
} else if (key == '6') {
num[spot] = 6;
println(num[spot]);
} else if (key == '7') {
num[spot] = 7;
println(num[spot]);
} else if (key == '8') {
num[spot] = 8;
println(num[spot]);
} else if (key == '9') {
num[spot] = 9;
println(num[spot]);
} else if (key == '+') {
num[spot] = 10;
println(num[spot]);
} else if (key == '-') {
num[spot] = 11;
println(num[spot]);
}
}
}
}
class Calculations {
int dice() {
int i = 0;
if (die == 1) {
i = round(random(2));
}
if (die == 2) {
i = round(random(3));
}
if (die == 3) {
i = round(random(4));
}
if (die == 4) {
i = round(random(6));
}
if (die == 5) {
i = round(random(8));
}
if (die == 6) {
i = round(random(10));
}
if (die == 7) {
i = round(random(12));
}
if (die == 8) {
i = round(random(20));
}
if (die == 9) {
i = round(random(100));
}
return i;
}
int finalcalc() {
int[] roll = new int[key];
int result = 0;
for (int i = 0; i > roll.length; i++) {
roll[i] = dice();
if (plusminus == true) {
result = dice() + modnum;
}
if (plusminus == false) {
result = dice() - modnum;
}
}
return result;
}
}
I've made sure that my arrays are initialized properly, and I made sure that each of my variables are being referenced correctly, but this hasn't changed anything. I'm not sure what else I need to do.
Here is the error:
java.lang.NullPointerException: Cannot invoke "Final_Project$Calculations.finalcalc()" because "this.c" is null
at Final_Project.startScreen(Final_Project.java:68)
at Final_Project.keyPressed(Final_Project.java:80)

It's missing : Calculations c= new Calculations();

Condtional statements using Calendar.HOUR_OF_DAY

I have this code and it has to show one of the strings based on the time of the day.
The code is
public void onTimeTick() {
mTime.setTimeInMillis(System.currentTimeMillis());
// Let's see what string we need according to the time
int saluteResId = R.string.salute_fallback;
if (mTime.get(Calendar.HOUR_OF_DAY) > 4) {
saluteResId = R.string.salute_morning;
} else if (mTime.get(Calendar.HOUR_OF_DAY) > 12) {
saluteResId = R.string.salute_evening;
} else if (mTime.get(Calendar.HOUR_OF_DAY) > 19 || mTime.get(Calendar.HOUR_OF_DAY) < 5) {
saluteResId = R.string.salute_night;
}
}
But the problem is that HOUR_OF_DAY will always remain greater than 4 so it will never even check the remaining two conditions and the string will always be set to salute_morning. I am not very good in java and trying to figure out how I can make the first condition false so it will check the other conditions and set the string according to them.

I think this can be helpful
if (mTime.get(Calendar.HOUR_OF_DAY) > 4 && mTime.get(Calendar.HOUR_OF_DAY) <= 12) {
//saluteResId = R.string.salute_morning;
} else if (mTime.get(Calendar.HOUR_OF_DAY) > 12 && mTime.get(Calendar.HOUR_OF_DAY) <= 19) {
//saluteResId = R.string.salute_evening;
} else if (mTime.get(Calendar.HOUR_OF_DAY) > 19 && mTime.get(Calendar.HOUR_OF_DAY) <= 4) {
//saluteResId = R.string.salute_night;
}

Try this code
final Calendar d = Calendar.getInstance();
final int hh = d.get(Calendar.HOUR_OF_DAY);
//try this way
String time = null;
if (hh == 0) {
time =("Salute_Night");
} else if (hh == 1) {
time =("Salute_Night");
} else if (hh == 2) {
time =("Salute_Night");
} else if (hh == 3) {
time =("Salute_Night");
} else if (hh == 4) {
time =("Salute_Night");
} else if (hh == 5) {
time =("Salute_Morning");
} else if (hh == 6) {
time =("Salute_Morning");
} else if (hh == 7) {
time =("Salute_Morning");
} else if (hh == 8) {
time =("Salute_Morning");
} else if (hh == 9) {
time =("Salute_Morning");
} else if (hh == 10) {
time =("Salute_Morning");
} else if (hh == 11) {
time =("Salute_Morning");
} else if (hh == 12) {
time =("Salute_Evening");
} else if (hh == 13) {
time =("Salute_Evening");
} else if (hh == 14) {
time =("Salute_Evening");
} else if (hh == 15) {
time =("Salute_Evening");
} else if (hh == 16) {
time =("Salute_Evening");
} else if (hh == 17) {
time =("Salute_Evening");
} else if (hh == 18) {
time =("Salute_Evening");
} else if (hh == 19) {
time =("Salute_Evening");
} else if (hh == 20) {
time =("Salute_Night");
} else if (hh == 21) {
time =("Salute_Night");
} else if (hh == 22) {
time =("Salute_Night");
} else if (hh == 23) {
time =("Salute_Night");
}
//your text view where you want it to display
textviewTimeOfDay.settext.(time);

Why won't an IF statement work with rounded floats and doubles?

I am trying to check if a user has inputted a double between 3.5 and 7. I have tried to use the actual double and Math.round();, as well as StrictMath.round(). I have also tried to parse the string inputted as a float but it didn't change anything. Here is the basic code I used:
import java.util.Scanner;
public class IfStatement {
public static void main(String[] args) {
//create a Scanner
Scanner input = new Scanner(System.in);
System.out.print("Enter first double: ");
double number = input.nextDouble();
if (isDouble(number)==true) {
double x = Double.parseDouble(number);
if (3.5 <= x <= 7) {
System.out.println("good");
} else {
System.out.println("incorrect input");
}
} else {
System.out.println("incorroct input");
}
}
public static booleen isDouble(String str) {
if (str == null) {
return false;
}
int length = str.length();
if (length == 0) {
return false;
}
int i = 0;
if (str.charAt(0) == '-') {
if (length == 1) {
return false;
}
++i;
}
int integerPartSize = 0;
int exponentPartSize = -1;
while (i < length) {
char c = str.charAt(i);
if (c < '0' || c > '9') {
if (c == '.' && integerPartSize > 0 && exponentPartSize == -1) {
exponentPartSize = 0;
} else {
return false;
}
} else if (exponentPartSize > -1) {
++exponentPartSize;
} else {
++integerPartSize;
}
++i;
}
if ((str.charAt(0) == '0' && i > 1 && exponentPartSize < 1)
|| exponentPartSize == 0 || (str.charAt(length - 1) == '.')) {
return false;
}
return true;
}
}
I have also tried making 3.5 3 in the if statement but got no dice. I just need a loose explanation and not a full solution.

I've edited your code.
boolean spelling
isDouble() takes a String
a <= x <= b chained expressions are not allowed in Java
Also,
if ((str.charAt(0) == '0' && i > 1 && exponentPartSize < 1) || exponentPartSize == 0 || (str.charAt(length - 1) == '.')) {
return false;
}
return true;
can be simplified to
return (str.charAt(0) != '0' || i <= 1 || exponentPartSize >= 1)
&& exponentPartSize != 0 && (str.charAt(length - 1) != '.');
Here's the full code.
class Test {
public static boolean isDouble(String str) {
if (str == null) {
return false;
}
int length = str.length();
if (length == 0) {
return false;
}
int i = 0;
if (str.charAt(0) == '-') {
if (length == 1) {
return false;
}
++i;
}
int integerPartSize = 0;
int exponentPartSize = -1;
while (i < length) {
char c = str.charAt(i);
if (c < '0' || c > '9') {
if (c == '.' && integerPartSize > 0 && exponentPartSize == -1) {
exponentPartSize = 0;
} else {
return false;
}
} else if (exponentPartSize > -1) {
++exponentPartSize;
} else {
++integerPartSize;
}
++i;
}
return (str.charAt(0) != '0' || i <= 1 || exponentPartSize >= 1)
&& exponentPartSize != 0 && (str.charAt(length - 1) != '.');
}
public static void main(String[] args) {
//create a Scanner
Scanner input = new Scanner(System.in);
System.out.print("Enter first double: ");
String number = input.nextLine();
if (isDouble(number)) {
double x = Double.parseDouble(number);
if (3.5 <= x && x <= 7) {
System.out.println("good");
} else {
System.out.println("incorrect input");
}
} else {
System.out.println("incorroct input");
}
}
}

best practice of compare a map of metadata with an object?

I have a map of metadata and Expression class:
Map<String , Object> metaDate;
public class Expression{
private List<UserCondition> conditions;
private LogicalOperationEnum; // and , or
getters/stters...
}
public classUserCondition{
private String fieldName;
private MathOperationEnum operation; // > , < , >= , <= , =
private Object value;
getters/setters...
}
Now I hav a method this method in my businessService class:
private boolean evaluate(Map<String, Object> userMetaData, Expression expression) {
if (expression.getLogicalOperation() == LogicalOperationEnum.and) {
for (UserCondition c : expression.getConditions()) {
if (c.getOperation().getName() == ">" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) <= 0) {
return false;
} else if (c.getOperation().getName() == "<" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) >= 0) {
return false;
} else if (c.getOperation().getName() == "<=" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) > 0) {
return false;
} else if (c.getOperation().getName() == ">=" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) < 0) {
return false;
} else{
return true;
}
}
} else if (expression.getLogicalOperation() == LogicalOperationEnum.or) {
for (UserCondition c : expression.getConditions()) {
if (c.getOperation().getName() == ">" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) > 0) {
return true;
} else if (c.getOperation().getName() == "<" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) < 0) {
return true;
} else if (c.getOperation().getName() == "<=" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) <= 0) {
return true;
} else if (c.getOperation().getName() == ">=" && String.valueOf(userMetaData.get(c.getField())).compareTo(String.valueOf(c.getValue())) >= 0) {
return true;
}
}
}
return false;
}
Now i think that this method can implement better than , but i don't know how can i do that?

trouble with yahtzee in java

I have to create the yahtzee game and its methods like full house, small straight, big straight, 3 of kind, 4 of kind , and chance. Now this is what i have done so far and i would like to know if my methods are right and also i'm having a hard time trying to figure out how to check if its yahtzee , 3 of kind, 4 of kind , etc and this is in my main method. The program consists of seven rolls, where every roll can have up to two sub-rolls
static final int NUM_RERROLS_ = 2;
static final int NUM_OF_DICE = 5;
static final int NUM_ROLLS_ = 7;
static final int[] dice = new int[NUM_OF_DICE];
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
rollDice();
for (int i = 0; i < NUM_RERROLS_; i++) {
if (gotYatzee()) {
break;
}
System.out.println(diceToString());
askUser();
System.out.println("Which dice do you want to reroll: ");
secondReroll(convert(keyboard.nextLine()));
}
System.out.println(diceToString());
if (gotYatzee()) {
System.out.println("You got Yatzee & 50 points!");
} else if (largeStraight() == true) {
System.out.println("You got large straight");
} else {
System.out.println("Sorry no large straight");
}
if (smallStraight() == true) {
System.out.println("You got smallStraight");
} else {
System.out.println("Sorry no small straight");
}
if (fullHouse() == true) {
System.out.println("You got full house");
} else {
System.out.println("Sorry no full house");
}
{
System.out.println("SORRY NO YAHTZEE");
}
if (askUser() == false) {
if (largeStraight() == true) {
System.out.println("You got large straight");
} else {
System.out.println("Sorry no large straight");
}
if (smallStraight() == true) {
System.out.println("You got smallStraight");
} else {
System.out.println("Sorry no small straight");
}
if (fullHouse() == true) {
System.out.println("You got full house");
} else {
System.out.println("Sorry no full house");
}
}
}
public static void rollDice() {
for (int i = 0; i < NUM_OF_DICE; i++) {
dice[i] = randomValue();
}
}
public static int randomValue() {
return (int) (Math.random() * 6 + 1);
}
public static String diceToString() {
String dado = "Here are your dice: ";
for (int element : dice) {
dado = dado + element + " ";
}
return dado;
}
public static boolean gotYatzee() {
for (int element : dice) {
if (element != dice[0]) {
return false;
}
}
return true;
}
public static void secondReroll(int[] newValue) {
for (int element : newValue) {
dice[element - 1] = randomValue();
}
}
public static int[] convert(String s) {
StringTokenizer st = new StringTokenizer(s);
int[] a = new int[st.countTokens()];
int i = 0;
while (st.hasMoreTokens()) {
a[i++] = Integer.parseInt(st.nextToken());
}
return a;
}
public static boolean Chance() {
for (int element : dice) {
int i = 0;
if (element != dice[i]) {
i++;
return false;
}
}
return true;
}
public static boolean smallStraight() {
for (int i = 1; i <= NUM_OF_DICE; i++) {
boolean b = false;
for (int j = 0; j < NUM_OF_DICE; j++) {
b = b || (dice[j] == i);
}
if (!b) {
return false;
}
}
return true;
}
public static boolean largeStraight() {
int[] i = new int[5];
i = dice;
sortArray(i);
if (((i[0] == 1) && (i[1] == 2) && (i[2] == 3) && (i[3] == 4) && (i[4] == 5))
|| ((i[0] == 2) && (i[1] == 3) && (i[2] == 4) && (i[3] == 5) && (i[4] == 6))
|| ((i[1] == 1) && (i[2] == 2) && (i[3] == 3) && (i[4] == 4) && (i[5] == 5))
|| ((i[1] == 2) && (i[2] == 3) && (i[3] == 4) && (i[4] == 5) && (i[5] == 6))) {
return true;
} else {
return false;
}
}
public static boolean askUser() {
Scanner keyboard = new Scanner(System.in);
int a = 0;
String yes = "Yes";
String no = "No";
System.out.println("Do you want to reroll the dice again: Yes or No? ");
String userInput;
userInput = keyboard.next();
if (userInput.equals(yes)) {
System.out.println("ALRIGHTY!!");
return true;
} else if (userInput.equals(no)) {
}
return false;
}
public static boolean threeKind() {
int[] a = new int[5];
a = dice;
sortArray(a);
if ((((a[0] == a[1]) && (a[1] == a[2])) // Three of a Kind
|| ((a[1] == a[2]) && ((a[2] == a[3])
|| (((a[2] == a[3]) && (a[3] == a[4]))))))) {
return true;
} else {
return false;
}
}
/*public static boolean fourKind(int[] dice) {
}
*/
public static int[] sortArray(int[] numbers) {
int stop;
for (stop = 0; stop < numbers.length; stop++) {
for (int i = 0; i < numbers.length - 1; i++) {
if (numbers[i] > numbers[i + 1]) {
swap(numbers, i, i + 1);
}
}
}
return numbers;
}
public static void swap(int[] numbers, int pos1, int pos2) {
int temp = numbers[pos1];
numbers[pos1] = numbers[pos2];
numbers[pos2] = temp;
}
public static boolean fullHouse() {
int[] a = new int[5];
a = dice;
sortArray(a);
if ((((a[0] == a[1]) && (a[1] == a[2])) && // Three of a Kind
(a[3] == a[4]) && // Two of a Kind
(a[2] != a[3]))
|| ((a[0] == a[1]) && // Two of a Kind
((a[2] == a[3]) && (a[3] == a[4])) && // Three of a Kind
(a[1] != a[2]))) {
return true;
} else {
return false;
}
}
}

basically i want to figure out a way to check if its full house, 3 of kind, 4 of kind , etc
You have 6 dice after three rolls. Sort the array of user-retained dice after the 3 rolls.
Yahtzee: ((die[0] == die[4]) || (die[1] == die[5]))
4 of a kind: ((die[0] == die[3]) || (die[1] == die[4] || (die[2] == die[5]))
Small straight, 3 tests (x = 3,4,5): ((die[x] - die[x-3]) == 3)
Large straight, 2 tests (x = 4,5): ((die[x] - die[x-4]) == 4)
etc.
Chance: Up to the user, right?
Unless I'm missing something (I'm a little rusty on Yatzee), this should be fairly straightforward.