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There are several things that can be done to prevent null pointer exceptions:

1. Always check for null values: Before performing any operation on a variable, it is necessary to check if it is null or not.

2. Use object-oriented programming principles: Applying object-oriented programming principles like encapsulation, inheritance, and polymorphism helps in reducing the risk of null pointer exceptions.

3. Initialize variables: Initialize variables with default values when declared, and if that's not possible, assign it a value as soon as possible in the code.

4. Use assertions: Assertions help to validate the assumptions of the code and validate that variables are not null.

5. Use try-catch blocks: Using try-catch blocks can help in handling null pointer exceptions.

6. Use Java 8 Optional: Java 8 introduced Optional, which is a container that may or may not contain a value. Using Optional ensures that the value is present before any operations are performed.

7. Use a framework: Popular frameworks like Spring and Guava provide libraries that help in reducing null pointer exceptions.