I have been trying to reset a static variable that will keep count when certain methods are run. I want to be able to reset the counter after I return the output of one of the methods. The getEfficency will pull the value just fine, but after I run the getEfficency I would like for the static variable to be reset to 0, so that my program can run the other compute method.
public class Sequence {
private static int efficencyCount;
public static int computeIterative(int n) {
efficencyCount++;
}
public static int computeRecursive() {
efficencyCount++;
}
public static int getEfficiency() {
return efficencyCount;
}
}
Just use a temp variable and set hour static to 0.
Also you should keep protected your static variables to avoid misuse of your variables lutside of your class.
public static int getEfficiency (){
int temp=efficiencyCount;
efficiencyCount=0;
return temp;
}
You can create a local variable and store the value of count temporarily. Reset the value of efficencyCount and return the value of local temporary count variable.
public static int getEfficiency() {
int count = efficencyCount;
efficencyCount = 0;
return count;
}
You could do it as below:
Create a method, and reset the efficencyCount variable inside this method
public static void resetCounter() {
efficencyCount = 0;
}
Create a temporary variable that holds the efficencyCount, then reset efficencyCount to zero.
public static int getEfficiency(){
int temp = efficencyCount;
efficencyCount = 0;
return temp;
}
Related
I working on a program where I need to count the how many objects are created by a certain class (and all its sub-classes). I made a quick test program that replicated my problem:
public class Test {
private int number = 0;
public Test(){
number++;
}
public int returnNumber(){
return number;
}
}
How do I make the variable 'number' save its value, instead of initializing every time I create a new object?
Make number static in order for it to have the same value for all instances of your class.
private static int number = 0
You might want to change your returnNumber to be static too.
If you want each instance of your class to have a unique number, you should keep that number in a separate member :
public class Test {
private int number = 0;
private static int counter = 0;
public Test(){
number = counter++;
}
public int getNumber() {
return number; // each instance will have a unique value
}
public static int getCounter () {
return counter; // this will return the current value of the counter
}
}
number needs to be a static type so its shared across all instances of your class.
Consider private static int number = 0 instead.
Better still, you ought to make number an atomic type, so multiple constructors can be called on several threads. (Otherwise you could end up underestimating number.)
Consider using AtomicInteger as the type; still static of course.
create variable as static
private static int number = 0;
Make it
private static int number = 0;
public class Test {
private static int number = 0;
public Test(){
number++;
}
public int returnNumber(){
return number;
}
}
public void run() {
moveTest();
}
private int moveTest() {
while (frontIsClear()) {
move();
for (int i = 0; i < 0; i++);
}
}
There is the code, I want to basically count the loop (in order to find the middle point of an straight line, and then store the count into an ' int ' and than use that int (value) in another private method (or public if it needs to).
Thanks in advance hope you guys can understand my point ^^
Your question is not clear and strange, but I thing you can just create a private field in a class, return the result of method moveTest in it, and then use it in another method...
Like:
private int count = 0;
public void run() {
count = moveTest();
// use 'count'variable
}
private void someMethodUsingCountVariable() {
int a = count;
}
Not to sure why the integers lowRange and highRange are not going between these classes.
package guessnumber;
public class GuessNumber
{
static public int computerGenedNumber;
static public int lowRange;
static public int highRange;
static public int playerGuess;
public static void main(String[] args)
{
Input.range(lowRange, highRange);
Rand.number(lowRange, highRange, computerGenedNumber);
Input.guess();
Give.result();
}
}
Next Class:
package guessnumber;
import javax.swing.JOptionPane;
class Input
{
public static void range(int lowRange, int highRange)
{
String rawUserInput;
rawUserInput = JOptionPane.showInputDialog("Please enter the range you wish to guess. (EX: 1-10)", "1-10");
for(int i = 0; i < rawUserInput.length(); i++)
{
if(rawUserInput.charAt(i) == '-')
{
lowRange = Integer.parseInt(rawUserInput.substring(0, i));
highRange = Integer.parseInt(rawUserInput.substring(i + 1, rawUserInput.length()));
}
}
}
static void guess()
{
}
}
And the last relevant one:
package guessnumber;
class Rand
{
static public void number(int lowRange, int highRange, int computerGenedNumber)
{
computerGenedNumber = (int)(Math.random() * (highRange - lowRange) + lowRange);
}
}
The rest of the classes are currently blank so I don't think I need to put them here too.
Here is a simplified piece of code which reproduce your problem, and make sure you understand why it is causing problem and the solution:
class Foo {
public static void square(int a, int result) {
result = a*a;
}
}
class Bar {
public static void main(String[] args) {
int a=2;
int result = 0;
Foo.square(a, result);
System.out.println("result " + result);
}
}
This should be fundamental understanding of Java. Checkout what is the meaning of "pass-by-value"
In brief, the parameter passed in the method is a copy of the argument. Therefore when you are changing the parameter in your method, you are just changing another piece of data, and your change is not reflected to caller.
One way to fix is to change the method and return your result, which looks like:
class Foo {
public static int square(int a) {
return a*a;
}
}
class Bar {
public static void main(String[] args) {
int a=2;
int result = 0;
result = Foo.square(a);
System.out.println("result " + result);
}
}
Another common solution is to pass in a "holder object" as the result. Although the object reference is passed by value, that copy of object reference is still pointing to the same object as caller. I won't go too deep into this as it is less common and you should be able to get the proper way doing so once you have better understanding on how value (including object reference) is passed around.
Parameters are passed "by value" in Java. What that means is that when you call
input.range(lowRange, highRange);
it gives the current values of those variables to input.range, but it doesn't give input.range a way to modify them. In the range method:
public static void range(int lowRange, int highRange)
the parameters lowRange and highRange (which have no connection with the variables in GuessNumber, even though the names are the same) are copies of what you pass in. When you assign lowRange = ... in the method, it changes the copy but has no effect at all on the lowRange and highRange in GuessNumber.
You need to write a range method that returns two values. This needs a little bit of work, but I'd write a Range class that has low and high members, and then change your method to
public static Range range()
That method would have to create a new Range object. I think it's OK for low and high to be public members of Range:
class Range {
public int low;
public int high;
public Range(int low, int high) {
this.low = low;
this.high = high;
}
}
Normally, public data in a class is a bad thing, but for a class whose only purpose is to let a method return multiple values, it's OK in my opinion.
I have a quick question out of curiosity...if I declare an integer in one method, for example: i = 1, is it possible for me to take that i and use its value in my main class (or another method)? The following code may be helpful in understanding what I'm asking...of course, the code might not be correct depending on what the answer is.
public class main {
public main() {
int n = 1;
System.out.print(n + i);
}
public number(){
i = 1;
}
}
No you cannot! Not unless you make it an instance variable!
Or actually send it to the function as an argument!
First, let's start simple. All methods that are not constructors require a return type. In other words,
public void number(){
i = 1;
}
would be more proper.
Second: the main method traditionally has a signature of public static void main(String[] args).
Now, on to your question at hand. Let's consider a few cases. I will be breaking a few common coding conventions to get my point across.
Case 1
public void number(){
i = 1;
}
As your code stands now, you will have a compile-time error because i is not ever declared. You could solve this by declaring this somewhere in the class. To access this variable, you will need an object of type Main, which would make your class look like this:
public class Main {
int i;
public static void main(String[] args) {
Main myMain = new Main();
myMain.number();
System.out.print(myMain.i);
}
public void number(){
i = 1;
}
}
Case 2
Let's say you don't want to make i a class variable. You just want it to be a value returned by the function. Your code would then look like this:
public class Main {
public static void main(String[] args) {
Main myMain = new Main();
System.out.print(myMain.number());
}
public int number(){ //the int here means we are returning an int
i = 1;
return i;
}
}
Case 3
Both of the previous cases will print out 1 as their output. But let's try something different.
public class Main {
int i = 0;
public static void main(String[] args) {
Main myMain = new Main();
myMain.number();
System.out.print(myMain.i);
}
public void number(){
int i = 1;
}
}
What do you think the output would be in this case? It's not 1! In this case, our output is 0. Why?
The statement int i = 1; in number(), it creates a new variable, also referred to as i, in the scope of number(). As soon as number() finishes, that variable is wiped out. The original i, declared right under public class Main has not changed. Thus, when we print out myMain.i, its value is 0.
Case 4
One more case, just for fun:
public class Main {
int i = 0;
public static void main(String[] args) {
Main myMain = new Main();
System.out.print(myMain.number());
System.out.print(myMain.i);
}
public int number(){
int i = 1;
return i;
}
}
What will the output of this be? It's 10. Why you ask? Because the i returned by number() is the i in the scope of number() and has a value of 1. myMain's i, however, remains unchanged as in Case 3.
You may use a class-scope field to store you variable in a class object or you can return it from one method or pass it as a parameter to the other. Mind that you will need to call your methods in the right order, which is not the best design possible.
public class main {
int n;
int i;
public main() {
n = 1;
System.out.print(n + i);
}
public number(){
i = 1;
}
}
Yes, create a classmember:
public class Main
{
private int i;
public main() {
int n = 1;
System.out.print(n + i);
number();
System.out.print(n + i);
}
public number(){
i = 1;
}
}
void method(){
int i = 0; //has only method scope and cannot be used outside it
}
void method1(){
i = 1; //cannot do this
}
This is because the scope of i is limited to the method it is declared in.
The question asks for the user to enter. lets forget about that and make it already initialized with some values so I can understand the first part.
Write a static method
public static int findMax(int[] r)
which receives as a parameter an array of numbers of type int and returns the maximum value.
Write a main method to test your program with array size 10 and elements entered by user.
Can't get what you exactly want to do? But if want that one class has static method and other class in main access that then you can try like this..
public class Demo {
public static void main(String[] args) {
int i = FindMaxClass.findMax(new int[10]); // pass int array
System.out.print(i);
}
}
class FindMaxClass{
public static int findMax(int[] r){
//logic to find max.
return 0; // return the max value found.
}
}
If static method should be in same class then others answers are good/correct.
public static int findMax(int[] values) {
int max = Integer.MIN_VALUE;
for (int val : values) {
if (val > max) {
max = val;
}
}
return max;
}
public static void main(String[] args) {
System.out.println("Max value: " + findMax(new int[]{1,2,3,1,2,3}));
}
I'm not going to write the code to solve your exact problem, but I'll tell you how to create and call a static method. See the example below:
public class Test {
// This is a static method
static void myMethod(int myArg) {
System.out.println("Inside Test.myMethod " + myArg);
}
// This is how to call it from main()
public static void main(String[] args) {
myMethod(3);
}
}
If you need more information to static methods take a look at:
http://openbook.galileocomputing.de/javainsel/javainsel_05_003.htm#mjd51d5220468ee4a1f2a07b6796bb393b
But you already know how to iterate over arrays?
Or maybe you are able to be more specific what you do not understand and what you have tried yet?