Reputation: 89
How to use a variable of one method in another method?
I want to know how can I use the variable a[i][j] in the method Scores() to use it in the methods MD() and sumD() in the following code:
In my code, the methods MD() and sumD() can't get the result.
public class Test3 {
public void Scores() {
double[][] a= new double[3][5];
int i,j;
for(i=0; i<3; i++ ){
for(j=0; j<5; j++){
a[i][j]= (double) Math.random();
System.out.println("a[" + i + "][" + j + "] = " +a[i][j]);
}
}
}
public void MD(){
double[][] b =new double[3][5];
int [] m = new int[5];
int i,j;
//double[][] a= new double[3][5];
for(j= 0; j<5; j++)
for(i=0 ; i<3 ; i++)
{
b[i][j]=0.0;
if(a[i][j]>0.0)
m[j]++;
}
for(j= 0; j<5; j++){
for(i=0 ; i<3 ; i++) {
if(a[i][j] > 0.0){
b[i][j]=a[i][j]*m[j];
System.out.println("b[" + i + "][" + j + "] = " + b[i][j]);
}
}
}
}
public void sumD(){
int i,j,n;
double[] sum= new double[3];
double[] k= new double[3];
//double[][] a= new double[3][5];
for(i=0; i<3; i++){
n=0;
sum[i]=0.0;
for(j=0; j<5; j++){
if(a[i][j]>0.0){
sum[i] += (a[i][j])*2;
n++;
}
}
k[i]=sum[i]/n;
System.out.println("k[" + i + "] = " + k[i]);
}
}
public static void main(String[] args){
Test3 print= new Test3();
print.Scores();
print.MD();
print.sumD();
}
}
Upvotes: 8
Views: 275467
Answers (9)
Reputation: 29
public class Practise {
String a;
public String getA() {
return a;
}
public void setA(String a) {
this.a = a;
}
void meth1(){
this.setA("asd");
System.out.println(a);
}
void meth2(){
String b="qwerty";
System.out.println(getA()+" "+b);
}
public static void main(String[] args) {
Practise p= new Practise();
p.meth1();
p.meth2();
}
}
Upvotes: -2
Reputation: 101
you can declare a 2-d array pointer as a member of the class. Then declare the size and value inside a member function. In this case you can access it form another function..
See the use of T[][] in this code
public class Knapsack {
//private static Scanner in;
int T[][];
int MaximumVal(int wt[],int val[], int total){
int l=total;
int m=val.length;
T = new int[m+1][l+1];
for (int i=0; i<=m; i++){
for(int j=0; j<=l; j++){
if(i==0 || j==0){
T[i][j]=0;
continue;
}
if(j-wt[i-1] >= 0){
T[i][j]=Math.max(T[i-1][j], val[i-1]+T[i-1][j-wt[i-1]]);
}
else{
T[i][j]=T[i-1][j];
}
}
}
return T[m][l];
}
void PrintPath(int wt[], int val[]){
int i=T.length-1;
int j=T[0].length-1;
while(j!=0){
if(i>0){
while(T[i][j]==T[i-1][j]){
i--;
}
}
System.out.print(wt[i-1]+" ");
j=j-wt[i-1];
i--;
}
}
//Main Function with test case ::
public static void main(String args[]){
int wt[]={1,3,4,5};
int val[]={1,4,5,7};
Knapsack K = new Knapsack();
System.out.print("Enter the total value: ");
//in = new Scanner(System.in);
//int total = in.nextInt();
int result = K.MaximumVal(wt,val,7); // pass total
System.out.println("Total value is "+ result);
K.PrintPath(wt,val);
}
}
Upvotes: 1
Reputation: 1
public class Test3 {
double[][] a=new double[3][5];
public void Scores() {
int i,j;
for(i=0; i<3; i++ ){
for(j=0; j<5; j++){
a[i][j]= (double) Math.random();
System.out.println("a[" + i + "][" + j + "] = " +a[i][j]);
}
}
}
public void MD(){
double[][] b =new double[3][5];
int [] m = new int[5];
int i,j;
//double[][] a= new double[3][5];
for(j= 0; j<5; j++)
for(i=0 ; i<3 ; i++)
{
b[i][j]=0.0;
if(a[i][j]>0.0)
m[j]++;
}
for(j= 0; j<5; j++){
for(i=0 ; i<3 ; i++) {
if(a[i][j] > 0.0){
b[i][j]=a[i][j]*m[j];
System.out.println("b[" + i + "][" + j + "] = " + b[i][j]);
}
}
}
}
public void sumD(){
int i,j,n;
double[] sum= new double[3];
double[] k= new double[3];
//double[][] a= new double[3][5];
for(i=0; i<3; i++){
n=0;
sum[i]=0.0;
for(j=0; j<5; j++){
if(a[i][j]>0.0){
sum[i] += (a[i][j])*2;
n++;
}
}
k[i]=sum[i]/n;
System.out.println("k[" + i + "] = " + k[i]);
}
}
public static void main(String[] args){
Test3 print= new Test3();
print.Scores();
print.MD();
print.sumD();
}
}
Upvotes: 0
Reputation:
Looks like you're using instance methods instead of static ones.
If you don't want to create an object, you should declare all your methods static, so something like
private static void methodName(Argument args...)
If you want a variable to be accessible by all these methods, you should initialise it outside the methods and to limit its scope, declare it private.
private static int[][] array = new int[3][5];
Global variables are usually looked down upon (especially for situations like your one) because in a large-scale program they can wreak havoc, so making it private will prevent some problems at the least.
Also, I'll say the usual: You should try to keep your code a bit tidy. Use descriptive class, method and variable names and keep your code neat (with proper indentation, linebreaks etc.) and consistent.
Here's a final (shortened) example of what your code should be like:
public class Test3 {
//Use this array in your methods
private static int[][] scores = new int[3][5];
/* Rather than just "Scores" name it so people know what
* to expect
*/
private static void createScores() {
//Code...
}
//Other methods...
/* Since you're now using static methods, you don't
* have to initialise an object and call its methods.
*/
public static void main(String[] args){
createScores();
MD(); //Don't know what these do
sumD(); //so I'll leave them.
}
}
Ideally, since you're using an array, you would create the array in the main method and pass it as an argument across each method, but explaining how that works is probably a whole new question on its own so I'll leave it at that.
Upvotes: 7
Reputation: 191
If you want to be able to use the 2d-matrix a, you need to declare it outside of your methods.
public class Test3 {
double[][] a= new double[3][5];
public void Scores() {
//double[][] a= new double[3][5];
int i,j;
for(i=0; i<3; i++ ){
for(j=0; j<5; j++){
a[i][j]= (double) Math.random();
System.out.println("a[" + i + "][" + j + "] = " +a[i][j]);
}
}
}
.......
You'll see that I've moved the declaration of a (formerly inside Scores(), and which I have commented out) outside the function, and it is now a field of the class Test3. When you declare a variable inside a function, it is local to that function. It cannot be seen by other functions, etc. If you declare it as a class field, your functions can see it. Take a look at this, as it may help. Language/VariableScope.htm">http://www.java2s.com/Tutorial/Java/0020_Language/VariableScope.htm The term "scope" just refers to the lifetime of a variable and where it can be seen. Hope this helps!
Upvotes: 0
Reputation: 11658
just make a[i][j] as class variable, declare it outside the Scores(), just below the class name
public class Test3 {
double[][] a= new double[3][5];
public void Scores() {
....
}
.....
}
Upvotes: 1
Reputation: 18359
Just move the declaration of a to make it a private property of class Test3, like this:
public class Test3 {
private double[][] a;
public void Scores() {
a= new double[3][5];
int i,j;
...etc...
Upvotes: 2
Reputation: 272667
You can't. Variables defined inside a method are local to that method.
If you want to share variables between methods, then you'll need to specify them as member variables of the class. Alternatively, you can pass them from one method to another as arguments (this isn't always applicable).
Upvotes: 17
Related Questions
- How to use an array in more than one method
- How to use array from one method in another?
- How can I use a defined Array variable from another method?
- Using variable from another method in Java
- Error when trying to use variable in different method
- How can I make it so that my variable is used throughout the whole method
- Java - Calling a method from another class with array as parameter
- I need to call an array from another method, then use it
- How to use variable from class inside method in java
- Using an array in a method that has been created in another method