src/main/java/xyz/zhouxy/plusone/commons/base/BoolRef.java

@@ -1,68 +0,0 @@
-/*
- * Copyright 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package xyz.zhouxy.plusone.commons.base;
-
-import com.google.common.annotations.Beta;
-
-import xyz.zhouxy.plusone.commons.function.BoolUnaryOperator;
-
-@Beta
-public class BoolRef {
-
-    private boolean value;
-
-    public BoolRef(boolean value) {
-        this.value = value;
-    }
-
-    public boolean getValue() {
-        return value;
-    }
-
-    public void setValue(boolean value) {
-        this.value = value;
-    }
-
-    public void apply(BoolUnaryOperator operator) {
-        this.value = operator.applyAsBool(this.value);
-    }
-
-    @Override
-    public String toString() {
-        return String.format("BoolRef[%s]", value);
-    }
-
-    @Override
-    public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        result = prime * result + (value ? 1231 : 1237);
-        return result;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj)
-            return true;
-        if (obj == null)
-            return false;
-        if (getClass() != obj.getClass())
-            return false;
-        return value == ((BoolRef) obj).value;
-    }
-
-}

src/main/java/xyz/zhouxy/plusone/commons/base/CharRef.java

@@ -1,68 +0,0 @@
-/*
- * Copyright 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package xyz.zhouxy.plusone.commons.base;
-
-import com.google.common.annotations.Beta;
-
-import xyz.zhouxy.plusone.commons.function.CharUnaryOperator;
-
-@Beta
-public class CharRef {
-
-    private char value;
-
-    public CharRef(char value) {
-        this.value = value;
-    }
-
-    public char getValue() {
-        return value;
-    }
-
-    public void setValue(char value) {
-        this.value = value;
-    }
-
-    public void apply(CharUnaryOperator operator) {
-        this.value = operator.applyAsChar(this.value);
-    }
-
-    @Override
-    public String toString() {
-        return String.format("CharRef[%s]", value);
-    }
-
-    @Override
-    public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        result = prime * result + value;
-        return result;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj)
-            return true;
-        if (obj == null)
-            return false;
-        if (getClass() != obj.getClass())
-            return false;
-        return value == ((CharRef) obj).value;
-    }
-
-}

src/main/java/xyz/zhouxy/plusone/commons/base/DoubleRef.java

@@ -1,71 +0,0 @@
-/*
- * Copyright 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package xyz.zhouxy.plusone.commons.base;
-
-import java.util.function.DoubleUnaryOperator;
-
-import com.google.common.annotations.Beta;
-
-@Beta
-public class DoubleRef {
-
-    private double value;
-
-    public DoubleRef(double value) {
-        this.value = value;
-    }
-
-    public double getValue() {
-        return value;
-    }
-
-    public void setValue(double value) {
-        this.value = value;
-    }
-
-    public void apply(DoubleUnaryOperator operator) {
-        this.value = operator.applyAsDouble(this.value);
-    }
-
-    @Override
-    public String toString() {
-        return String.format("DoubleRef[%s]", value);
-    }
-
-    @Override
-    public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        long temp;
-        temp = Double.doubleToLongBits(value);
-        result = prime * result + (int) (temp ^ (temp >>> 32));
-        return result;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj)
-            return true;
-        if (obj == null)
-            return false;
-        if (getClass() != obj.getClass())
-            return false;
-        final DoubleRef other = (DoubleRef) obj;
-        return Double.doubleToLongBits(value) == Double.doubleToLongBits(other.value);
-    }
-
-}

src/main/java/xyz/zhouxy/plusone/commons/base/IntRef.java

@@ -1,68 +0,0 @@
-/*
- * Copyright 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package xyz.zhouxy.plusone.commons.base;
-
-import java.util.function.IntUnaryOperator;
-
-import com.google.common.annotations.Beta;
-
-@Beta
-public class IntRef {
-
-    private int value;
-
-    public IntRef(int value) {
-        this.value = value;
-    }
-
-    public int getValue() {
-        return value;
-    }
-
-    public void setValue(int value) {
-        this.value = value;
-    }
-
-    public void apply(IntUnaryOperator operator) {
-        this.value = operator.applyAsInt(this.value);
-    }
-
-    @Override
-    public String toString() {
-        return String.format("IntRef[%s]", value);
-    }
-
-    @Override
-    public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        result = prime * result + value;
-        return result;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj)
-            return true;
-        if (obj == null)
-            return false;
-        if (getClass() != obj.getClass())
-            return false;
-        return value == ((IntRef) obj).value;
-    }
-
-}

src/main/java/xyz/zhouxy/plusone/commons/base/LongRef.java

@@ -1,68 +0,0 @@
-/*
- * Copyright 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package xyz.zhouxy.plusone.commons.base;
-
-import java.util.function.LongUnaryOperator;
-
-import com.google.common.annotations.Beta;
-
-@Beta
-public class LongRef {
-
-    private long value;
-
-    public LongRef(long value) {
-        this.value = value;
-    }
-
-    public long getValue() {
-        return value;
-    }
-
-    public void setValue(long value) {
-        this.value = value;
-    }
-
-    public void apply(LongUnaryOperator operator) {
-        this.value = operator.applyAsLong(this.value);
-    }
-
-    @Override
-    public String toString() {
-        return String.format("LongRef[%s]", value);
-    }
-
-    @Override
-    public int hashCode() {
-        final int prime = 31;
-        int result = 1;
-        result = prime * result + (int) (value ^ (value >>> 32));
-        return result;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj)
-            return true;
-        if (obj == null)
-            return false;
-        if (getClass() != obj.getClass())
-            return false;
-        return value == ((LongRef) obj).value;
-    }
-
-}

src/main/java/xyz/zhouxy/plusone/commons/base/Ref.java

@@ -18,35 +18,100 @@ package xyz.zhouxy.plusone.commons.base;
 
 import java.util.Objects;
 import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Predicate;
 import java.util.function.UnaryOperator;
 
-import com.google.common.annotations.Beta;
+import javax.annotation.Nullable;
 
-@Beta
+/**
+ * {@link Ref} 包装了一个值，表示对该值的应用。
+ *
+ * <p>灵感来自于 C# 的 {@value ref} 参数修饰符。C# 允许通过以下方式，将值返回给调用端：</p>
+ * <pre>
+ * void Method(ref int refArgument)
+ * {
+ *     refArgument = refArgument + 44;
+ * }
+ *
+ * int number = 1;
+ * Method(ref number);
+ * Console.WriteLine(number); // Output: 45
+ * </pre>
+ * {@link Ref} 使 Java 可以达到类似的效果，如：
+ * <pre>
+ * void method(final Ref&lt;Integer&gt; refArgument) {
+ *     refArgument.transformValue(i -&gt; i + 44);
+ * }
+ *
+ * Ref&lt;Integer&gt; number = Ref.of(1);
+ * method(number);
+ * System.out.println(number.getValue()); // Output: 45
+ * </pre>
+ * <p>
+ * 当一个方法需要产生多个结果时，无法有多个返回值，可以使用 {@link Ref} 作为参数传入，方法内部修改 {@link Ref} 的值。
+ * 调用方在调用方法之后，使用 {@code getValue()} 获取结果。
+ * </p>
+ * <pre>
+ * String method(final Ref&lt;Integer&gt; intRefArgument, final Ref&lt;String&gt; strRefArgument) {
+ *     intRefArgument.transformValue(i -&gt; i + 44);
+ *     strRefArgument.setValue("Hello " + strRefArgument.getValue());
+ *     return "Return string";
+ * }
+ *
+ * Ref&lt;Integer&gt; number = Ref.of(1);
+ * Ref&lt;String&gt; str = Ref.of("Java");
+ * String result = method(number, str);
+ * System.out.println(number.getValue()); // Output: 45
+ * System.out.println(str.getValue()); // Output: Hello Java
+ * System.out.println(result); // Output: Return string
+ * </pre>
+ *
+ * @author <a href="http://zhouxy.xyz:3000/ZhouXY108">ZhouXY</a>
+ * @since 1.0.0
+ */
 public final class Ref<T> {
 
+    @Nullable
     private T value;
 
-    public Ref() {
-        this.value = null;
-    }
-
-    public Ref(T value) {
+    private Ref(@Nullable T value) {
         this.value = value;
     }
 
+    public static <T> Ref<T> of(@Nullable T value) {
+        return new Ref<>(value);
+    }
+
+    public static <T> Ref<T> empty() {
+        return new Ref<>(null);
+    }
+
+    @Nullable
     public T getValue() {
         return value;
     }
 
-    public void setValue(T value) {
+    public void setValue(@Nullable T value) {
         this.value = value;
     }
 
-    public void transform(UnaryOperator<T> operator) {
+    public void transformValue(UnaryOperator<T> operator) {
         this.value = operator.apply(this.value);
     }
 
+    public <R> Ref<R> transform(Function<? super T, R> function) {
+        return Ref.of(function.apply(this.value));
+    }
+
+    public boolean checkValue(Predicate<? super T> predicate) {
+        return predicate.test(this.value);
+    }
+
+    public void execute(Consumer<? super T> consumer) {
+        consumer.accept(value);
+    }
+
     public boolean isNull() {
         return this.value == null;
     }
@@ -55,10 +120,6 @@ public final class Ref<T> {
         return this.value != null;
     }
 
-    public void execute(Consumer<? super T> consumer) {
-        consumer.accept(value);
-    }
-
     @Override
     public String toString() {
         return String.format("Ref[%s]", value);
@@ -73,7 +134,7 @@ public final class Ref<T> {
     }
 
     @Override
-    public boolean equals(Object obj) {
+    public boolean equals(@Nullable Object obj) {
         if (this == obj)
             return true;
         if (obj == null)

src/test/java/xyz/zhouxy/plusone/commons/base/RefTests.java

@@ -27,78 +27,20 @@ class RefTests {
 
     @Test
     void testRef() {
-        Ref<String> strRef = new Ref<>("ZhouXY");
+        Ref<String> strRef = Ref.of("ZhouXY");
+        assertTrue(strRef.checkValue("ZhouXY"::equals));
+        assertFalse(strRef.checkValue("ZhouXY1"::equals));
         apply(strRef);
         assertEquals("Hello ZhouXY", strRef.getValue());
+        assertTrue(strRef.checkValue("Hello ZhouXY"::equals));
         log.info("strRef: {}", strRef);
+
+        Ref<String> intStringRef = Ref.of("108");
+        Ref<Integer> integerRef = intStringRef.transform(Integer::parseInt);
+        assertEquals(108, integerRef.getValue());
     }
 
     void apply(Ref<String> strRef) {
-        strRef.transform(str -> "Hello " + str);
-    }
-
-    @Test
-    void testBoolRef() {
-        BoolRef boolRef = new BoolRef(false);
-        apply(boolRef);
-        assertTrue(boolRef.getValue());
-        log.info("boolRef: {}", boolRef);
-    }
-
-    void apply(BoolRef boolRef) {
-        boolRef.setValue(true);
-    }
-
-    @Test
-    void testCharRef() {
-        CharRef charRef = new CharRef('T');
-
-        apply(false, charRef);
-        assertEquals('0', charRef.getValue());
-        log.info("charRef: {}", charRef);
-
-        apply(true, charRef);
-        assertEquals('1', charRef.getValue());
-        log.info("charRef: {}", charRef);
-    }
-
-    void apply(boolean condition, CharRef charRef) {
-        charRef.apply(c -> condition ? '1' : '0');
-    }
-
-    @Test
-    void testDoubleRef() {
-        DoubleRef doubleRef = new DoubleRef(2.33);
-        apply(88.108, doubleRef);
-        assertEquals(2.33 * 88.108, doubleRef.getValue());
-        log.info("doubleRef: {}", doubleRef);
-    }
-
-    void apply(double num, DoubleRef doubleRef) {
-        doubleRef.apply(d -> d * num);
-    }
-
-    @Test
-    void testIntRef() {
-        IntRef intRef = new IntRef(108);
-        apply(88, intRef);
-        assertEquals(108 - 88, intRef.getValue());
-        log.info("intRef: {}", intRef);
-    }
-
-    void apply(int num, IntRef intRef) {
-        intRef.apply(d -> d - num);
-    }
-
-    @Test
-    void testLongRef() {
-        LongRef longRef = new LongRef(108L);
-        apply(88L, longRef);
-        assertEquals(108L + 88L, longRef.getValue());
-        log.info("intRef: {}", longRef);
-    }
-
-    void apply(long num, LongRef longRef) {
-        longRef.apply(d -> d + num);
+        strRef.transformValue(str -> "Hello " + str);
     }
 }