I have found a case in which the "Introduce Method" refactoring generates invalid code.  It appears to have a problem when a single statement declares several variables, such as:

    double foo, bar, baz, bat, wuux;

To reproduce this, add the following code to a method within a Java class (I used the main method for a newly-generated class:

        double leftH, rightH, delta, deltaY;
        double tLeft, tRight, bLeft, bRight;
        
        tLeft = 3.4;
        tRight = 4.5;
        bLeft = 5.6;
        bRight = 6.7;
        
        leftH = Math.max(tLeft, bLeft);
        rightH = Math.max(tRight, bRight);
        delta = rightH - leftH;

Highlight all of this code and right-click, then select Refactor -> Introduce Method from the popup menu.  Type a name for the new method (I used "foo") and click OK on the dialog.  This generates the following new method:

    private static void foo(double rightH, double leftH) {
        double delta;
        double leftH, rightH, delta, deltaY;
        double tLeft,
        double tLeft, tRight,
        double tLeft, tRight, bLeft,
        double tLeft, tRight, bLeft, bRight;
        tLeft = 3.4;
        tRight = 4.5;
        bLeft = 5.6;
        bRight = 6.7;
        leftH = Math.max(tLeft, bLeft);
        rightH = Math.max(tRight, bRight);
        delta = rightH - leftH;
    }

As you can see, the tLeft variable is declared multiple times and all of these except for the last are invalid statements since they do not conclude with a semicolon.