How to make a method return type as Callable<Boolean>

Question

In one of my methods:

public void pageIsReady()

the implementation is

Awaitility.await().atMost(5, TimeUnit.SECONDS).until(isPageLoaded());

Here, isPageLoaded() method returns boolean value, but I want it to return a Callable of Boolean, because the until() method in Awaitility expects Callable<Boolean>.

Please help me to make the method isPageLoaded() return Callable<Boolean>

Here is the implementation of isPageLoaded() method:

protected Boolean isPageLoaded() {
    String jsQuery = "function pageLoaded() "
            + "{var loadingStatus=(document.readyState=='complete');"
            + "return loadingStatus;};"
            + "return pageLoaded()";

    boolean isSuccess = false;
    try {
        isSuccess = (Boolean) evaluateJavascript(jsQuery);
    } catch (Exception exp) {
        exp.printStackTrace();
    }
    return isSuccess;
}

Answer 1

The easiest way to do that is to use a method reference Callable<Boolean> isPageLoaded = this::isPageLoaded, or to use it explicitly as lambda Callable<Boolean> isPageLoaded = () -> isPageLoaded();

This would look like

Awaitility.await().atMost(5, TimeUnit.SECONDS).until(this::isPageLoaded);
Awaitility.await().atMost(5, TimeUnit.SECONDS).until(() -> isPageLoaded());

Another way would be to define your method as returning a Callable<Boolean> and then using lambda syntax () -> {} to write the callable.

protected Callable<Boolean> isPageLoaded() {
    return () -> {
        String jsQuery = "function pageLoaded() "
            + "{var loadingStatus=(document.readyState=='complete');"
            + "return loadingStatus;};"
            + "return pageLoaded()";

        boolean isSuccess = false;
        try {
            isSuccess = (Boolean) evaluateJavascript(jsQuery);
        } catch (Exception exp) {
            exp.printStackTrace();
        }
        return isSuccess;
    };
}

Lambda expressions and method references can be quite powerful tools.