throw和throws的区别？

package constxiong.interview;
 
import java.io.IOException;
 
public class TestThrowsThrow {
 
    public static void main(String[] args) {
        testThrows();
        
        Integer i = null;
        testThrow(i);
        
        String filePath = null;
        try {
            testThrow(filePath);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 测试 throws 关键字
     * @throws NullPointerException
     */
    public static void testThrows() throws NullPointerException {
        Integer i = null;
        System.out.println(i + 1);
    }
    
    /**
     * 测试 throw 关键字抛出 运行时异常
     * @param i
     */
    public static void testThrow(Integer i) {
        if (i == null) {
            throw new NullPointerException();//运行时异常不需要在方法上申明
        }
    }
    
    /**
     * 测试 throw 关键字抛出 非运行时异常，需要方法体需要加 throws 异常抛出申明
     * @param i
     */
    public static void testThrow(String filePath) throws IOException {
        if (filePath == null) {
            throw new IOException();//运行时异常不需要在方法上申明
        }
    }
}