I'm new to java and I was wondering if there was a way to access a variable from one method in another method. While writing a program using methods, I realized that I cannot just take one variable from one method and use it in another method. So I was wondering if there was a way to do this.
Here is my code so far
import java.util.Scanner;
public class program{
public static void mass(){
double a,e,p,v;
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the volume: ");
v=scanner.nextDouble();
p=0.8;
System.out.println("Enter the alcohol volume:(in percents) ");
e=scanner.nextDouble();
e=e/100;
a=v*e*p;
System.out.println("mass is: " a);
}
public static void Concentration(){
double w,r,m;
String person;
System.out.println("Enter the person: m for male, f for female, j for teenager ");
Scanner sc=new Scanner(System.in);
person=sc.nextLine();
switch(person){
case "m": r=0.7;
break;
case "f": r=0.6;
break;
case "j": r=0.5;
break;
}
System.out.println("Enter person's weight: ");
m=sc.nextDouble();
//w=a/(m*r); //a from the method mass
}
public static void main(String[]args){
mass();
Concentration();
/*If(w>=0.5){ //w from the method concentration
System.out.println("You cannot drive!");
Else{
System.out.println("You can drive");
}
} */
}
}
CodePudding user response：
There are two kinds of variables:
- local variables (block-scoped)
- member variables (class/instance level scope)
See: https://www.geeksforgeeks.org/variable-scope-in-java/
So, if you want to reuse a variable accross multiple methods, then you will need to convert it from a local variable into a member variable. In your case you only use static methods, so a would be declared outside your methods as
static double a;
and avoid declaring it inside your mass method, so your declaration line would be changed to
double e,p,v;
Note that the a is missing to avoid variable shadowing.
You may want to change your methods to instance-level methods, in which case you can declare a without the static keyword, depending on your plans and needs.
Also, a well-known approach is to implement getters and setters in order to make sure that whenever you get or set a value, if there are common operations, then they are implemented only once instead of code repeating.
Below you see the simplest changes to your code to achieve the goal you have specified:
import java.util.Scanner;
public class program{
static double a;
public static void mass(){
double e,p,v;
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the volume: ");
v=scanner.nextDouble();
p=0.8;
System.out.println("Enter the alcohol volume:(in percents) ");
e=scanner.nextDouble();
e=e/100;
a=v*e*p;
System.out.println("mass is: " a);
}
public static void Concentration(){
double w,r,m;
String person;
System.out.println("Enter the person: m for male, f for female, j for teenager ");
Scanner sc=new Scanner(System.in);
person=sc.nextLine();
switch(person){
case "m": r=0.7;
break;
case "f": r=0.6;
break;
case "j": r=0.5;
break;
}
System.out.println("Enter person's weight: ");
m=sc.nextDouble();
w=a/(m*r); //a from the method mass
}
public static void main(String[]args){
mass();
Concentration();
/*If(w>=0.5){ //w from the method concentration
System.out.println("You cannot drive!");
Else{
System.out.println("You can drive");
}
} */
}
}
Finally, you could also use a as a return value, like:
import java.util.Scanner;
public class program{
public static double mass(){
double a,e,p,v;
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the volume: ");
v=scanner.nextDouble();
p=0.8;
System.out.println("Enter the alcohol volume:(in percents) ");
e=scanner.nextDouble();
e=e/100;
a=v*e*p;
System.out.println("mass is: " a);
return a;
}
public static void Concentration(double a){
double w,r,m;
String person;
System.out.println("Enter the person: m for male, f for female, j for teenager ");
Scanner sc=new Scanner(System.in);
person=sc.nextLine();
switch(person){
case "m": r=0.7;
break;
case "f": r=0.6;
break;
case "j": r=0.5;
break;
}
System.out.println("Enter person's weight: ");
m=sc.nextDouble();
//w=a/(m*r); //a from the method mass
}
public static void main(String[]args){
Concentration(mass());
/*If(w>=0.5){ //w from the method concentration
System.out.println("You cannot drive!");
Else{
System.out.println("You can drive");
}
} */
}
}
CodePudding user response：
To make a variable accessible in all functions of the class you can static the variable in question in the current class
package javaapplication6;
import java.util.Scanner;
// @author Vulembere
public class JavaApplication6 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
mass();
Concentration();
if (w >= 0.5) {
System.out.println("You cannot drive!");
} else {
System.out.println("You can drive");
}
}
static double w;
public static void mass() {
double a, e, p, v;
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the volume: ");
v = scanner.nextDouble();
p = 0.8;
System.out.println("Enter the alcohol volume:(in percents) ");
e = scanner.nextDouble();
e = e / 100;
a = v * e * p;
System.out.println("mass is: " a);
}
public static void Concentration() {
double r, m;
String person;
System.out.println("Enter the person: m for male, f for female, j for teenager ");
Scanner sc = new Scanner(System.in);
person = sc.nextLine();
switch (person) {
case "m":
r = 0.7;
break;
case "f":
r = 0.6;
break;
case "j":
r = 0.5;
break;
}
System.out.println("Enter person's weight: ");
m = sc.nextDouble();
//w=a/(m*r); //a from the method mass
}
}