Anonymous
Anonymous
inner classes make it easier to pass around code as data.

package com.minte9.lambdas.expressions;
import javax.swing.JButton;
import javax.swing.JFrame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Anonimous {
public static void main(String[] args) {
JFrame frame = new JFrame();
JButton button = new JButton("Click me");
button.addActionListener(
new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("Button clicked");
}
}
);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(button);
frame.setSize(300, 300);
frame.setVisible(true);
}
}
Behavior
Starting with Java 8 we can use lambdas expressions, to
pass behavior not objects.

package com.minte9.lambdas.expressions;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Behavior {
public static void main(String[] args) {
JFrame frame = new JFrame();
JButton button = new JButton("Click me");
button.addActionListener(
event -> System.out.println("Button clicked")
);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(button);
frame.setSize(300, 300);
frame.setVisible(true);
}
}
Lambdas
There are
different ways of writing lambda expressions.

package com.minte9.lambdas.expressions;
import java.util.function.BinaryOperator;
public class Lambdas {
public static void main(String[] args) {
Runnable noArgs = () -> System.out.println("Hello World");
new Thread(noArgs).run();
Runnable multiStatement = () -> {
System.out.println("Hello");
System.out.println("World");
};
new Thread(multiStatement).run();
BinaryOperator<Integer> op = (x, y) -> x + y;
System.out.println(op.apply(2, 3));
}
}
Final Variable
To use a variable
from outside an anonymous inner class it must be final.

package com.minte9.lambdas.expressions;
import java.util.Arrays;
import javax.xml.ws.Holder;
public class FinalVariable {
public static void main(String[] args) {
Holder<Integer> holder = new Holder<>(0);
Arrays.asList("a", "b", "c").forEach((x) -> {
holder.value ++;
});
System.out.println(holder.value);
final String str = "A";
Arrays.asList("a", "b", "c").forEach((x) -> {
});
System.out.println(str);
}
}
Type inference
Javac
type inference is smart, but it needs enought information.

package com.minte9.lambdas.expressions;
import java.util.function.Function;
public class TypeInference {
public static void main(String[] args) {
Function<Long, Long> op = x -> x + 1;
System.out.println(op.apply(20L));
}
}