Java Coding Editor for Technical Interviews

Running OpenJDK 16 - Autocomplete is enabled

You should define a public class named Solution with a public static void main. Your code is compiled with -Xlint (linting) and run with -ea (assertions enabled).

A few libraries are included for your convenience, and are available on the classpath with no additional work from you. Simply import and fire away:

json-simple for parsing/encoding JSON.

The google code project page has some useful examples.

guava provides immutable collections and other handy utility classes.
Apache Commons Lang for assorted utilities.

Has a bunch of useful stuff like date parsing. The import prefix is org.apache.commons.lang3, so you can perform imports by writing import org.apache.commons.lang3.ArrayUtils.

JUnit, the gold standard for testing in Java. If you want to ask your candidate to write JUnit-style tests during the interview, please format your Java code like so:

  import org.junit.*;
  import org.junit.runner.*;

  public class Solution {
    @Test
    public void testNoop() {
      Assert.assertTrue(true);
    }

    public static void main(String[] args) {
      JUnitCore.main("Solution");
    }
  }
Code language: Java (java)

Stack traces originating from JUnit errors are trimmed for brevity.

In the future we may auto-detect the existence of @Test annotations, so stay tuned.

jMock, a library to assist with mocking in Java. Combining jMock with the previous JUnit example:

  import org.jmock.*;
  import org.junit.*;
  import org.junit.runner.*;

  interface Receiver {
    void receive(String message);
  }

  public class Solution {
    @Test
    public void testMock() {
      Mockery context = new Mockery();
      Receiver receiver = context.mock(Receiver.class);
      context.checking(new Expectations() {{
        oneOf (receiver).receive("hello");
      }});
      receiver.receive("hello");
      context.assertIsSatisfied();
    }

    public static void main(String[] args) {
      JUnitCore.main("Solution");
    }
  }
Code language: Java (java)

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