Define a Java class to solve this problem:
Given a String and a Character, remove all instances of the Character in the String

Solve this two ways:

1. Iterate through the String, one character at a time
   
2. Find a method in the String class that can solve this in one line
   

Write methods for each solution.

Afterwards, write a TestNG or JUnit class for each solution which tests these methods.
Include both positive and negative cases for validations.

1. Test code is located in the test folder
2. This is a maven project
3. pom.xml has required dependencies
4. Source code is located in the main folder
5. Test cases file name: TestcasesStringProblem