檔案目錄
./
+- src
+- test
| +- org
| +- ruoxue
| +- java_147
| +- functional
| +- consumer
| +- ConsumerFunctionalTest.java 單元測試
Consumer Functional Interface 提供方法引用、參考等操作 Java Consumer Functional Interface 。
Food
Consumer Functional Interface 建立 Food 類別，覆寫 equals 、 hashCode ，定義屬性和方法，用來建立一個物件。
@NoArgsConstructor
@Getter
@Setter
@Builder
public static class Food {
private String name;
private double quantity;
private int type;
public Food(String name, double quantity, int type) {
this.name = name;
this.quantity = quantity;
this.type = type;
}
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this, ToStringStyle.JSON_STYLE);
builder.appendSuper(super.toString());
builder.append("name", name);
builder.append("quantity", quantity);
builder.append("type", type);
return builder.toString();
}
public boolean equals(Object object) {
if (!(object instanceof Food)) {
return false;
}
if (this == object) {
return true;
}
Food other = (Food) object;
return new EqualsBuilder().append(getName(), other.getName()).isEquals();
}
public int hashCode() {
return new HashCodeBuilder().append(getName()).toHashCode();
}
}
methodReference
Consumer Functional Interface 建立一個 Consumer ，引用其他方法為實例，循環訪問印出元素。
@Test
public void methodReference() {
List<String> list = Arrays.asList("Bacon", "", "Ham", "Pork", "");
Consumer<String> println = System.out::println;
list.stream().forEach(println);
List<Food> foodList = Arrays.asList(new Food("Bacon", 1, 1), null, new Food("Ham", 2, 1),
new Food("Pork", 3, 1), null);
Consumer<Food> nonNull = o -> System.out.println(Objects.nonNull(o));
Consumer<Food> contains = o -> {
Optional<Food> opt = Optional.ofNullable(o);
opt.ifPresent(e -> System.out.println(e.name.contains("o")));
};
foodList.stream().forEach(nonNull.andThen(contains));
}
Bacon
Ham
Pork
true
true
false
true
false
true
true
falsemethodParameter
Functional Interface Consumer in Java 建立一個 Consumer ，當作其他方法的傳入參數，循環訪問印出元素。
public static void forEach(List<String> list, Consumer<String> consumer) {
list.stream().forEach(consumer);
}
public static void foodForEach(List<Food> list, Consumer<Food> consumer) {
list.stream().forEach(consumer);
}
@Test
public void methodParameter() {
List<String> list = Arrays.asList("Bacon", "Ham", "Pork");
Consumer<String> lengthGreaterThan = s -> System.out.println(s.length() > 3);
forEach(list, lengthGreaterThan);
List<Food> foodList = Arrays.asList(new Food("Bacon", 1, 1), new Food("Ham", 2, 1), new Food("Pork", 3, 1));
Consumer<Food> lengthLessThan = o -> System.out.println(o.name.length() < 6);
Consumer<Food> contains = o -> System.out.println(o.name.contains("o"));
foodForEach(foodList, lengthLessThan.andThen(contains));
}Bacon
Ham
Pork
true
true
false
true
false
true
true
falseConsumerFunctionalTest.java
Functional Interface Consumer in Java 新增單元測試，驗證 Java Consumer Functional Interface 是否符合預期。
package org.ruoxue.java_147.functional.consumer;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Consumer;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;
import org.junit.Test;
import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
public class ConsumerFunctionalTest {
@NoArgsConstructor
@Getter
@Setter
@Builder
public static class Food {
private String name;
private double quantity;
private int type;
public Food(String name, double quantity, int type) {
this.name = name;
this.quantity = quantity;
this.type = type;
}
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this, ToStringStyle.JSON_STYLE);
builder.appendSuper(super.toString());
builder.append("name", name);
builder.append("quantity", quantity);
builder.append("type", type);
return builder.toString();
}
public boolean equals(Object object) {
if (!(object instanceof Food)) {
return false;
}
if (this == object) {
return true;
}
Food other = (Food) object;
return new EqualsBuilder().append(getName(), other.getName()).isEquals();
}
public int hashCode() {
return new HashCodeBuilder().append(getName()).toHashCode();
}
}
@Test
public void methodReference() {
List<String> list = Arrays.asList("Bacon", "", "Ham", "Pork", "");
Consumer<String> println = System.out::println;
list.stream().forEach(println);
List<Food> foodList = Arrays.asList(new Food("Bacon", 1, 1), null, new Food("Ham", 2, 1),
new Food("Pork", 3, 1), null);
Consumer<Food> nonNull = o -> System.out.println(Objects.nonNull(o));
Consumer<Food> contains = o -> {
Optional<Food> opt = Optional.ofNullable(o);
opt.ifPresent(e -> System.out.println(e.name.contains("o")));
};
foodList.stream().forEach(nonNull.andThen(contains));
}
public static void forEach(List<String> list, Consumer<String> consumer) {
list.stream().forEach(consumer);
}
public static void foodForEach(List<Food> list, Consumer<Food> consumer) {
list.stream().forEach(consumer);
}
@Test
public void methodParameter() {
List<String> list = Arrays.asList("Bacon", "Ham", "Pork");
Consumer<String> lengthGreaterThan = s -> System.out.println(s.length() > 3);
forEach(list, lengthGreaterThan);
List<Food> foodList = Arrays.asList(new Food("Bacon", 1, 1), new Food("Ham", 2, 1), new Food("Pork", 3, 1));
Consumer<Food> lengthLessThan = o -> System.out.println(o.name.length() < 6);
Consumer<Food> contains = o -> System.out.println(o.name.contains("o"));
foodForEach(foodList, lengthLessThan.andThen(contains));
}
}
心得分享
Java Consumer Functional Interface 除了傳統實作接口的方法，使用 Lambda 表達式實作功能，能讓程式碼更加簡潔與直接，大幅提高可讀性， Functional Interface Consumer in Java 提供了幾種 Consumer 常見方法的操作範例。
