How to call a method of another class using codemodel

I have a java class say Class A with some methods already present, I am generating a class using code model say classB and while generating using code model I am trying to call one the method of that classA.

i tried below

method
    .body()
    .invoke(JExpr.ref(helper), "display")
    .arg("hello");

but it is not working, I will really appreciate if someone knows how to do the same

I want to generate a method like:

public void method() { 
    Helper helper = new Helper(); 
    helper.display("hello") 
}

I am also interested in how I can generate the following method:

@Test 
public void method() { 
    Assert.fail("message") 

}

Let's start with:

public void method() { 
    Helper helper = new Helper(); 
    helper.display("hello") 
}

Assuming you already have a JMethod method, you first need to create a helper instance:

JVar helper = method
    .body()
    .decl(
        codeModel.ref(Helper.class),
        "helper",
        JExpr._new(codeModel.ref(Helper.class)));

Then just invoke the desired method on it:

method
    .body()
    .invoke(helper, "display")
    .arg("hello");

No this one:

@Test
public void method() { 
    Assert.fail("message") 
}

It's even easier, you only have to do a static invocation. Something along the lines:

method
    .body()
    .staticInvoke(codeModel.ref(Assert.class))
    .arg("message");

If you're interested in the annotation:

method
    .annotate(Test.class);

Note that in the invocations above I could pass strings to the arg method directly (arg("message")). This is just a convenience method for strings. If you want to use other types like primitve types, you will need to do something like JExpr.lit(12.34).