How Can I Pass Functions as Parameters in Java?

Function as parameter in Java

In Java, how to pass a function as parameter to another function?

Java 8 and above

Use Java 8 lambda expression, when you have a class or interface (sometimes called a SAM type) with only one abstract method, for example:

public interface MyInterface {
    String doSomething(int param1, String param2);
}

then you can use a lambda expression instead where MyInterface is used:

class MyClass {
    public MyInterface myInterface = (p1, p2) -> { return p2 + p1; };
}

For example, you can To execute quickly by creating a new thread:

new Thread(() -> someMethod()).start();

and use method reference syntax to make it more concise:

new Thread(this::someMethod).start();

If does not use lambda expression formula, the last two examples will look like this:

new Thread(new Runnable() { someMethod(); }).start();

Java Pre-8 versions

A common pattern is to "wrap" a function inside an interface, such as Callable, and then pass a Callable:

public T myMethod(Callable<T> func) {
    return func.call();
}

This pattern is called the command pattern .

Remember that it is best to create interfaces for specific purposes. If you choose to use call, replace T above with any type of return value you expect, such as String.

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