Java中Consumer与Supplier接口的使用及区别小结

import java.util.function.Consumer;
import java.util.Arrays;
import java.util.List;

public class ConsumerExample {
    public static void main(String[] args) {
        // 基本用法
        Consumer<String> printConsumer = s -> System.out.println(s);
        printConsumer.accept("Hello Consumer!");
        
        // 方法引用方式
        Consumer<String> methodRefConsumer = System.out::println;
        methodRefConsumer.accept("Hello Method Reference!");
        
        // 集合遍历中的应用
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
        names.forEach(printConsumer);
        
        // andThen 方法组合多个 Consumer
        Consumer<String> upperCaseConsumer = s -> System.out.println(s.toUpperCase());
        Consumer<String> decoratedConsumer = s -> System.out.println("*** " + s + " ***");
        
        Consumer<String> combinedConsumer = upperCaseConsumer.andThen(decoratedConsumer);
        combinedConsumer.accept("functional interface");
        
        // 在 Optional 中的使用
        java.util.Optional<String> optional = java.util.Optional.of("Present");
        optional.ifPresent(combinedConsumer);
    }
}

import java.util.function.Supplier;
import java.util.List;
import java.util.Random;
import java.util.stream.Stream;

public class SupplierExample {
    public static void main(String[] args) {
        // 基本用法
        Supplier<String> stringSupplier = () -> "Hello from Supplier!";
        System.out.println(stringSupplier.get());
        
        // 方法引用方式
        Supplier<Double> randomSupplier = Math::random;
        System.out.println("Random number: " + randomSupplier.get());
        
        // 对象工厂
        Supplier<List<String>> listSupplier = () -> java.util.Arrays.asList("A", "B", "C");
        System.out.println("List from supplier: " + listSupplier.get());
        
        // 延迟计算/初始化
        Supplier<ExpensiveObject> expensiveObjectSupplier = () -> {
            System.out.println("Creating expensive object...");
            return new ExpensiveObject();
        };
        
        System.out.println("Supplier created but no object yet...");
        // 只有在调用 get() 时才会创建对象
        ExpensiveObject obj = expensiveObjectSupplier.get();
        
        // 在 Stream 中生成无限流
        Supplier<Integer> randomIntSupplier = () -> new Random().nextInt(100);
        Stream.generate(randomIntSupplier)
              .limit(5)
              .forEach(System.out::println);
              
        // 在 Optional 中作为备选值
        java.util.Optional<String> emptyOptional = java.util.Optional.empty();
        String value = emptyOptional.orElseGet(() -> "Default from supplier");
        System.out.println("Value from empty optional: " + value);
    }
    
    static class ExpensiveObject {
        ExpensiveObject() {
            // 模拟耗时操作
            try { Thread.sleep(1000); } catch (InterruptedException e) {}
        }
    }
}

import java.util.function.Consumer;
import java.util.function.Supplier;
import java.util.logging.Logger;

public class CombinedExample {
    private static final Logger logger = Logger.getLogger(CombinedExample.class.getName());
    
    public static void main(String[] args) {
        // 创建一个数据处理器，结合了 Supplier 和 Consumer
        processData(
            () -> { // Supplier - 提供数据
                // 模拟从数据库或API获取数据
                return new String[] {"Data1", "Data2", "Data3"};
            },
            data -> { // Consumer - 处理数据
                for (String item : data) {
                    System.out.println("Processing: " + item);
                }
            },
            error -> { // Consumer - 错误处理
                logger.severe("Error occurred: " + error.getMessage());
            }
        );
    }
    
    public static <T> void processData(Supplier<T> dataSupplier, 
                                      Consumer<T> dataProcessor, 
                                      Consumer<Exception> errorHandler) {
        try {
            T data = dataSupplier.get(); // 从Supplier获取数据
            dataProcessor.accept(data);  // 用Consumer处理数据
        } catch (Exception e) {
            errorHandler.accept(e);      // 用Consumer处理错误
        }
    }
}