What do @SuppressWarnings(“deprecation”) and (“unused”) mean in Java?

Question

What do these lines in my Java or Android project mean?

@SuppressWarnings(\"deprecation\")
@SuppressWarnings(\"unused\")

Answer 1

One more thing: you can not only add them inline, but also annotate methods. F.ex.

@Override
@SuppressWarnings("deprecation")
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    addPreferencesFromResource(R.xml.preferences);
}

Yet, it is recommended to use the smallest scope possible

As a matter of style, programmers should always use this annotation on the most deeply nested element where it is effective. If you want to suppress a warning in a particular method, you should annotate that method rather than its class.

Answer 2

In Java, @SuppressWarnings are use to restrict the compiler to show the certain warning on the console screen.

E.g

@SuppressWarnings("unused")
CheckBox transferredField = new CheckBox("is transferred");

if I don't use transferredField variable in my code then your Eclipse IDE never show the warning that you are not using this transferredField variable in your code.

Answer 3

the @SuppressWarnings("unused") and others i have tried,but it don't work,and i always use the method say gradle in this project to

lintOptions{
        checkReleaseBuilds false
        abortOnError  false;
        disable 'deprecation'
    }

    tasks.withType(JavaCompile) {
        options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
    }

Answer 4

The @SuppressWarnings annotation disables certain compiler warnings. In this case, the warning about deprecated code ("deprecation") and unused local variables or unused private methods ("unused"). This article explains the possible values.