Java Interview Questions

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N points lie on a circle. You draw lines connecting all the points to each other. These lines divide up the circle into a number of regions. How many regions is this? Assume that the points are scattered in such a way as to give the maximum number of regions for that N.
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Quantitative Trader

Interviewed at Jane Street

4.4
Jan 2, 2010

N points lie on a circle. You draw lines connecting all the points to each other. These lines divide up the circle into a number of regions. How many regions is this? Assume that the points are scattered in such a way as to give the maximum number of regions for that N.

3) Poker. 26 red, 26 black. Take one every time, you can choose to guess whether it’s red. You have only one chance. If you are right, you get 1 dollar. What’s the strategy? And what’s the expected earn?
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Quantitative Researcher Summer Intern

Interviewed at Jane Street

4.4
Apr 18, 2011

3) Poker. 26 red, 26 black. Take one every time, you can choose to guess whether it’s red. You have only one chance. If you are right, you get 1 dollar. What’s the strategy? And what’s the expected earn?

class A { public A() { foo(); } public void foo() { System.out.println("Class A"); } } class B extends A { public B(){} public void foo() { System.out.println("Class B"); } } class main { public static void main(String[] args) { A a = new B(); } } What does it print? Class A or Class B?
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Software Engineer

Interviewed at Bloomberg

4
Oct 25, 2012

class A { public A() { foo(); } public void foo() { System.out.println("Class A"); } } class B extends A { public B(){} public void foo() { System.out.println("Class B"); } } class main { public static void main(String[] args) { A a = new B(); } } What does it print? Class A or Class B?

There is a table that tracks every time a user turns a feature on or off, with columns user_id, action ("on" or "off), date, and time. How many users turned the feature on today? How many users have ever turned the feature on? In a table that tracks the status of every user every day, how would you add today's data to it?
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Data Scientist

Interviewed at Meta

3.5
Mar 29, 2017

There is a table that tracks every time a user turns a feature on or off, with columns user_id, action ("on" or "off), date, and time. How many users turned the feature on today? How many users have ever turned the feature on? In a table that tracks the status of every user every day, how would you add today's data to it?

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