In Java, to import whole classes of a package you can use import package.* syntax:

import java.util.*;

In C# it should be

import java.util;

Also, to import single class of a package in Java, name of that class is brought after package name:

import java.util.List;

but in C#, we should use aliases.

using List = java.util.List;

[Java]

package Test;

import junit.framework.*; 
import java.lang.StringBuffer;

public class Test
{
}

[C#]

namespace Test
{
    using junit.framework; 
    using StringBuffer = java.lang.StringBuffer;

    public class Test
    {
    }
}