🏷 Interfaces
4 patterns
Topic: Interfaces
All Java patterns related to Interfaces — java.evolved
Language
Private interface methods
Old
interface Logger {
default void logInfo(String msg) {
System.out.println(
"[INFO] " + timestamp() + msg);
}
default void logWarn(String msg) {
System.out.println(
"[WARN] " + timestamp() + msg);
}
}
Modern
interface Logger {
private String format(String lvl, String msg) {
return "[" + lvl + "] " + timestamp() + msg;
}
default void logInfo(String msg) {
IO.println(format("INFO", msg));
}
default void logWarn(String msg) {
IO.println(format("WARN", msg));
}
}
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JDK 9+
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Language
Anonymous classes to lambdas and method references
Old
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent event) {
save(event);
}
});
Modern
button.addActionListener(this::save);
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JDK 8+
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Language
Default interface methods
Old
// Need abstract class to share behavior
public abstract class AbstractLogger {
public void log(String msg) {
System.out.println(
timestamp() + ": " + msg);
}
abstract String timestamp();
}
// Single inheritance only
public class FileLogger
extends AbstractLogger { ... }
Modern
public interface Logger {
default void log(String msg) {
IO.println(
timestamp() + ": " + msg);
}
String timestamp();
}
// Multiple interfaces allowed
public class FileLogger
implements Logger, Closeable { ... }
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JDK 8+
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Language
Static methods in interfaces
Old
// Separate utility class needed
public class ValidatorUtils {
public static boolean isBlank(
String s) {
return s == null ||
s.trim().isEmpty();
}
}
// Usage
if (ValidatorUtils.isBlank(input)) { ... }
Modern
public interface Validator {
boolean validate(String s);
static boolean isBlank(String s) {
return s == null ||
s.trim().isEmpty();
}
}
// Usage
if (Validator.isBlank(input)) { ... }
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JDK 8+
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