Interpretation of Java usage code

Java usage code

is a static method in the Java standard library, located inin class.

This method is used to check whether the given object reference is non-empty (i.e. notnull）。

The basic usage is as follows:

public static boolean nonNull(Object obj) {
    return obj != null;
}

Example of usage:

import ;

public class Example {
    public void someMethod(String input) {
        if ((input)) {
            // Action performed when the input is not null            ("Input is not null, its value: " + input);
        } else {
            throw new IllegalArgumentException("Input cannot be null");
        }
    }
}

// use:Example example = new Example();
String someString = "Hello";
(someString); // If someString is not null, the message will be printed
// Or used as a predicate in stream operationsList&lt;String&gt; list = ...; // Assume it is a list of strings()
    .filter(Objects::nonNull)
    .forEach(::println); // This will print only the list of non null Elements

Notice:

()The method does not throw an exception, it simply returns a boolean value indicating whether the object is not empty.
If you need to throw an exception when the object is null, you should use()method, which will be thrown when the incoming object is nullNullPointerException。

() and ()

contrast:

Traditional writing	Objects Method	Applicable scenarios
if (user != null)	if ((user))	Forward operation (Logistics are executed only when the object exists)
if (user == null)	if ((user))	Reverse operation (provides alternate logic when the object is empty)

Examples of using Stream streams:

List&lt;String&gt; names = ()
    .filter(Objects::nonNull) // Filter null user objects    .map(User::getName)
    .collect(());

Summarize

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