Execute two separate test cases in the same browser instance using TestNG xml file

Question

I have two testcases in two separate java classes, 1. login and 2. add new item. I want to execute both as separate testcases under the same browser instance. Ideally one browser window will open, and execute the login testcase. After login, the second testcases will continue to execute under the same browser. I am currently using TestNG xml file to run these tests. Following is the <classes> tag within xml file that contains both classes.

<classes>

<class name="com.SeleniumFramework.testCases.TC_Login" />

<class name="com.SeleniumFramework.testCases.TC_AddItem" />

</classes>