java_upgrade/src/main/java/lambdas/FileFilterDemo.java at master · sairam-github/java_upgrade · GitHub

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package lambdas;

import java.io.File;

import java.io.FileFilter;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.function.Consumer;

import java.util.function.DoubleSupplier;

import java.util.function.Function;

import java.util.logging.Logger;

public class FileFilterDemo {

public static void main(String[] args) {

File srcDir = new File("src/main/java");

File[] files = srcDir.listFiles();

for (File f : files) {

System.out.println(f);

}

System.out.println("Using a file filter to return directories only");

files = srcDir.listFiles(new FileFilter() {

@Override

public boolean accept(File pathname) {

return pathname.isDirectory();

}

});

for (File f : files) {

System.out.println(f);

}

// compiler: what are the listFiles overloads?

// do any take functional interfaces as arguments?

// if so, do any of the single abstract methods match the

// signature of the provided lambda expression?

FileFilter filter = pathname -> pathname.isDirectory();

files = srcDir.listFiles(filter);

for (File f : files) {

System.out.println(f);

}

filter = File::isDirectory;

files = srcDir.listFiles(filter);

for (File f : files) {

System.out.println(f);

}

Logger log = Logger.getLogger(FileFilterDemo.class.getName());

Consumer<String> printer = x -> System.out.println("The value of x is " + x);

Consumer<String> logger = log::info;

Consumer<String> printAndLog = printer.andThen(logger);

List<String> strings = new ArrayList<>();

strings.add("this");

strings.add("is");

strings.add("a");

strings.add("list");

strings.add("of");

strings.add("strings");

// List.of("this", "is", "a", "list", "of", "strings")

// .forEach(printAndLog);

strings.forEach(printAndLog);

DoubleSupplier random = Math::random;

strings.stream()

.map(String::length)

.forEach(System.out::println);

}

java_upgrade/src/main/java/lambdas/FileFilterDemo.java at master · sairam-github/java_upgrade · GitHub

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