[java] How to make a boolean variable switch between true and false every time a method is invoked?

var logged_in = false;
logged_in = !logged_in;

A little example:

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var logged_in = false;_x000D_
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$("#enable").click(function() {_x000D_
    logged_in = !logged_in;_x000D_
    checkLogin();_x000D_
});_x000D_
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function checkLogin(){_x000D_
    if (logged_in)_x000D_
        $("#id_test").removeClass("test").addClass("test_hidde");_x000D_
    else_x000D_
        $("#id_test").removeClass("test_hidde").addClass("test");_x000D_
    $("#id_test").text($("#id_test").text()+', '+logged_in);_x000D_
}
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.test{_x000D_
    color: red;_x000D_
    font-size: 16px;_x000D_
    width: 100000px_x000D_
}_x000D_
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.test_hidde{_x000D_
    color: #000;_x000D_
    font-size: 26px;_x000D_
}
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<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<div class="test" id="id_test">Some Content...</div>_x000D_
<div style="display: none" id="id_test">Some Other Content...</div>_x000D_
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<div>_x000D_
    <button id="enable">Edit</button>_x000D_
</div>
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