添加流 API

src/main/java/xyz/zhouxy/plusone/commons/seq/Seq.java

@@ -0,0 +1,133 @@
+package xyz.zhouxy.plusone.commons.seq;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.StringJoiner;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Predicate;
+
+import com.google.common.annotations.Beta;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+
+@Beta
+@FunctionalInterface
+public interface Seq<T> extends Consumer<Consumer<T>> {
+    // 这个方法和 forEach 是完全等价的
+    void accept(Consumer<T> consumer);
+
+    static <T> Seq<T> from(Collection<T> collection) {
+        return collection::forEach;
+    }
+
+    static <T> Seq<T> unit(T t) {
+        return c -> c.accept(t);
+    }
+
+    default <E> Seq<E> map(Function<T, E> func) {
+        Seq<T> srcSeq = this;
+        return c -> srcSeq.accept((T t) -> c.accept(func.apply(t)));
+    }
+
+    default <E> Seq<E> flatMap(Function<T, Seq<E>> function) {
+        Seq<T> srcSeq = this;
+        return c -> srcSeq.accept(t -> function.apply(t).accept(c));
+    }
+
+    default Seq<T> filter(Predicate<T> predicate) {
+        Seq<T> srcSeq = this;
+        return (Consumer<T> c) -> srcSeq.accept((T t) -> {
+            if (predicate.test(t)) {
+                c.accept(t);
+            }
+        });
+    }
+
+    static void stop() {
+        throw StopException.INSTANCE;
+    }
+
+    default void consumeTillStop(Consumer<T> consumer) {
+        try {
+            accept(consumer);
+        } catch (StopException ignore) {
+            // ignore
+        }
+    }
+
+    default Seq<T> take(int n) {
+        return c -> {
+            int[] i = { n };
+            consumeTillStop(t -> {
+                if (i[0]-- > 0) {
+                    c.accept(t);
+                } else {
+                    stop();
+                }
+            });
+        };
+    }
+
+    default Seq<T> drop(int n) {
+        return c -> {
+            int[] a = { n - 1 };
+            accept(t -> {
+                if (a[0] < 0) {
+                    c.accept(t);
+                } else {
+                    a[0]--;
+                }
+            });
+        };
+    }
+
+    default Seq<T> onEach(Consumer<T> consumer) {
+        Seq<T> srcSeq = this;
+        return c -> srcSeq.accept(consumer.andThen(c));
+    }
+
+    default <E, R> Seq<R> zip(Iterable<E> iterable, BiFunction<T, E, R> function) {
+        return c -> {
+            Iterator<E> iterator = iterable.iterator();
+            consumeTillStop(t -> {
+                if (iterator.hasNext()) {
+                    c.accept(function.apply(t, iterator.next()));
+                } else {
+                    stop();
+                }
+            });
+        };
+    }
+
+    default String join(String sep) {
+        StringJoiner joiner = new StringJoiner(sep);
+        accept(t -> joiner.add(t.toString()));
+        return joiner.toString();
+    }
+
+    default List<T> toList() {
+        ImmutableList.Builder<T> builder = ImmutableList.builder();
+        accept(builder::add);
+        return builder.build();
+    }
+
+    default Set<T> toSet() {
+        ImmutableSet.Builder<T> set = ImmutableSet.builder();
+        accept(set::add);
+        return set.build();
+    }
+
+    static class StopException extends RuntimeException {
+        private static final long serialVersionUID = -8975705275260458012L;
+        private static final StopException INSTANCE = new StopException();
+
+        @Override
+        public synchronized Throwable fillInStackTrace() {
+            return this;
+        }
+    }
+}

src/test/java/xyz/zhouxy/plusone/commons/seq/SeqTests.java

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+package xyz.zhouxy.plusone.commons.seq;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.function.Consumer;
+
+import org.junit.jupiter.api.Test;
+
+import com.google.common.collect.ImmutableList;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+class SeqTests {
+
+    @Test
+    void testSeq() {
+        List<Integer> list = ImmutableList.of(108, 2333, 666, 555, 1, 2, 3, 23, 78, 65, 77, 22, 108);
+        List<String> result = new ArrayList<>();
+        Seq<String> targetSeq = new Seq<String>() {
+            @Override
+            public void accept(Consumer<String> c) {
+                list.forEach(t -> {
+                    c.accept(String.valueOf(t + 250));
+                });
+            }
+        };
+        targetSeq.accept(result::add);
+        // list.forEach(t -> {
+        // result.add(t + 250 + "");
+        // });
+        log.info("{}", result);
+
+        for (Integer i : produceEvenNumbers(9)) {
+            System.out.print(i);
+            System.out.print(" ");
+        }
+        System.out.println();
+        
+        Set<String> set = new TreeSet<>();
+        Seq<String> s = result::forEach;
+        s.accept(set::add);
+        log.info("{}", set);
+    }
+
+    Iterable<Integer> produceEvenNumbers(int upto) {
+        Seq<Integer> seq = c -> {
+            for (int i = 0; i <= upto; i += 2) {
+                c.accept(i);
+            }
+        };
+        return seq.toList();
+    }
+}