Berkshire Hathaway (BRK.A) CEO Warren Buffett says even though IBM has underperformed the market, he has no regrets buying IBM instead of Apple shares. When asked if the stock market was overvalued and if investors should worry about a correction, Buffet responded that if you worry about a correction, you shouldn't be in the market. He says investors should buy something they like, at a price they like, and then hold it for 20 years. Buffett, who is always on the hunt for acquisitions, also says he'd like to buy something "sooner rather than later." During his annual meeting, he mentioned that he'd be interested in buying more local car dealerships and possibly making an acquisition in Germany in the next five years. This year Berkshire Hathaway will increase its investment in renewable energy, but Buffett says that renewables are not a great investment for the individual investors. Buffett will also invest more in his railroad BNSF, as new federal rules were released on rail safety. He also defended his acquisition partner 3G Capital, after shareholders criticized 3G's practices of laying off workers. On the economy, Buffett says he thinks it will be difficult for the Federal Reserve to push up interest rates here in the U.S. this year, given the negative interest rates in Europe. Buffett still carries a flip phone, and when asked if he'd like a smartphone for his birthday he answered "I haven't thought about it." Buffett spoke with TheStreet's Rhonda Schaffler in Omaha, Nebraska.