How to call a method from a given string in Java

Question

I am trying to reduce my code from using a bunch of if statements from getting a specified command and calling a method for it.

Instead, I want to try something that would take that command and call a method name with it

Something like this:

"get" + commandString + "Count"()

Instead of:

if (command == "something") {
   callSomeMethod();
}

if (command == "somethingelse") {
   callSomeOtherMethod();
}

...

Is there a way to call a method from a specified string? Or a better way to approach this problem.

You can use reflection as shown in this duplicate question stackoverflow.com/questions/160970/… But you probably don't want to do that. — bhspencer
– bhspencer, Commented Mar 9, 2022 at 18:02
Does this answer your question? How do I invoke a Java method when given the method name as a string? — bhspencer
– bhspencer, Commented Mar 9, 2022 at 18:03

Captain Giraffe · Accepted Answer · 2022-03-09 18:03:21Z

2

This is the use-case for a switch case statement.

switch(command){
    case "command1": command1(); break;
    case "command2": command2(); break;

Using a string javascript style is fortunately impossible in Java. The comments links to answers how to use reflection to accomplish something similar. This is rarely a good solution.

answered Mar 9, 2022 at 18:03

Captain Giraffe

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1 Comment

Xanthan Over a year ago

Thanks for this. I forgot about the switch case. It kind of sucks Java doesn't have something like that.

Rakib Hasan · Accepted Answer · 2022-03-09 18:44:04Z

we can use

java.lang.reflect.Method Something like

java.lang.reflect.Method method;
try {
    method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..);
} catch (SecurityException e) { ... }
catch (NoSuchMethodException e) { ... }

The parameters identify the very specific method you need (if there are several overloaded available, if the method has no arguments, only give methodName).

And your possible solution can be like -

package com.test.pkg;
public class MethodClass {
  public int getFishCount() {
    return 5;
 }
 public int getRiceCount() {
    return 100;
 }
 public int getVegetableCount() {
    return 50;
 }
}

package com.test.pkg;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Test {
    public static void main(String[] args) {
        MethodClass classObj = new MethodClass();
        Method method;
        String commandString = "Fish";
        try {
            String methodName = "get" + commandString + "Count";
            method = classObj.getClass().getMethod(methodName);
            System.out.println(method.invoke(classObj));          //equivalent to System.out.println(testObj.getFishCount());
        } catch (SecurityException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
            e.printStackTrace();
        }
    }
}

Ref: How do I invoke a Java method when given the method name as a string?

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