Null pointer exception in Java - how to solve java.lang.NullPointerException?

In the process of Java development, it is inevitable to encounter the null pointer exception. Null pointer exception means that when the program tries to access a null object or empty array, a java.lang.NullPointerException exception will be thrown. This exception often crashes our program. I believe that most Java programmers should have encountered this exception, and because it is so common, we should learn how to solve the null pointer exception.

1. Using the assertion (assert) statement

The assertion (assert) statement in Java is used to check the logic errors of the program. In the Java language, the format of the assertion statement is as follows:

assert conditional expression;

If the value of the conditional expression is false, the program ends normally and a java.lang.AssertionError is thrown. abnormal. We can use this mechanism to avoid null pointer exceptions. If an object may be null, we can check before using the object, as follows:

assert obj != null;

If the assertion fails, an exception will be thrown, but In this case, the program's exception handling mechanism does not catch exceptions by default and needs to be adjusted according to the actual situation.

2. Using if statements

In programs, we often use if statements to check whether the object is empty. As shown below:

if (obj != null) {
// Operate the object
}

This method is relatively basic and very practical, but when Using multiple nullable objects requires a lot of if statements, which is not very elegant.

3. Use the ternary operator

The ternary operator in Java can simplify the writing of if statements, as shown below:

obj == null ? "" : obj.toString();

The above statement means: if obj is an empty object, return an empty string; otherwise, return the value of obj.toString().

4. Use try/catch statement

The try/catch statement in Java can also be used to handle null pointer exceptions. If some operations may cause a NullPointerException, we can do it in a try block and handle the exception in a catch block as follows:

try {

//进行处理

} catch (NullPointerException e) {

//处理空指针异常

}

Summary:

The occurrence of null pointer exception is a situation often encountered during program development, but we can solve this through the above method question. Assertions, if statements, ternary operators, and try/catch statements can effectively prevent the occurrence of null pointer exceptions and make the program more robust. In the process of writing programs, we should always remember to prevent the occurrence of null pointer exceptions and improve the reliability and stability of the program.

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