Table of Contents
ToggleOptional orElse vs orElseGet in Java
容器方法 orElse 傳入參數為泛型 T , orElseGet 傳入參數則為 Supplier 的功能接口, Optional 這兩個方法,非常相似,可能會引起混淆,都是如果值存在,則傳回值,不存在時,則傳回其他值, Optional orElseGet vs orElse in Java 本篇增加了範例,並透過單元測試來驗證產出結果。
public T orElse(T other) {
}
public T orElseGet(Supplier<? extends T> other) {
}
檔案目錄
./
+- src
+- test
| +- org
| +- ruoxue
| +- java_147
| +- optional
| +- OptionalOrElseVSOrElseGet.java
單元測試
Java Optional orElse vs orElseGet 提供 orElse 、 orElseGet 等操作。
static
初始化靜態類別,提供隨機數、預設值 List 。
private static SecureRandom secureRandom = null;
public static final String SHA1PRNG = "SHA1PRNG";
public static List<Food> defaultValues = Arrays.asList(new Food("DEFAULT_Beef", 1, 1),
new Food("DEFAULT_Chicken", 2, 1), new Food("DEFAULT_Duck", 3, 1));
static {
new Static();
}
protected static class Static {
public Static() {
try {
secureRandom = SecureRandom.getInstance(SHA1PRNG);
secureRandom.setSeed(System.nanoTime());
} catch (NoSuchAlgorithmException ex) {
ex.printStackTrace();
}
}
}
Food
Java Optional orElse vs orElseGet 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
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();
}
}
orElse
Java Optional orElse vs orElseGet 建立 Optional 容器,取得容器內的值,若值為 Null 則傳回預設值,值如果存在,一樣會調用 getDefaultValue 方法,比較沒有效率。
public static Food getDefaultValue() {
System.out.println("Call getDefaultValue()");
int index = secureRandom.nextInt(defaultValues.size());
return defaultValues.get(index);
}
@Test
@BenchmarkOptions(benchmarkRounds = 1, warmupRounds = 0, concurrency = 1)
public void orElse() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElse(getDefaultValue());
System.out.println(result);
assertEquals("Beef", result.getName());
}
Call getDefaultValue()
{"name":"Beef","quantity":1.0,"type":1}
OptionalOrElseVSOrElseGet.orElse: [measured 1 out of 1 rounds, threads: 1 (sequential)]
round: 0.02 [+- 0.00], round.block: 0.00 [+- 0.00], round.gc: 0.00 [+- 0.00], GC.calls: 0, GC.time: 0.00, time.total: 0.02, time.warmup: 0.00, time.bench: 0.02
orElseGet
Java Optional orElse vs orElseGet 建立 Optional 容器,取得容器內的值,若值為 Null 則傳回預設值,值如果存在,不會調用 getDefaultValue 方法。
@Test
@BenchmarkOptions(benchmarkRounds = 1, warmupRounds = 0, concurrency = 1)
public void orElseGet() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElseGet(() -> getDefaultValue());
System.out.println(result);
assertEquals("Beef", result.getName());
}
{"name":"Beef","quantity":1.0,"type":1}
OptionalOrElseVSOrElseGet.orElseGet: [measured 1 out of 1 rounds, threads: 1 (sequential)]
round: 0.05 [+- 0.00], round.block: 0.00 [+- 0.00], round.gc: 0.00 [+- 0.00], GC.calls: 0, GC.time: 0.00, time.total: 0.05, time.warmup: 0.00, time.bench: 0.05
orElseBenchmark
Java Optional orElseGet vs orElse 建立 Optional 容器,取得容器內的值,若值為 Null 則傳回預設值,值如果存在,一樣會調用 getDefaultValue 方法,比較沒有效率,執行 100 萬次,效能測試。
public static Food defaultValue() {
int index = secureRandom.nextInt(defaultValues.size());
return defaultValues.get(index);
}
@Test
@BenchmarkOptions(benchmarkRounds = 1000000, warmupRounds = 1, concurrency = 1)
public void orElseBenchmark() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElse(defaultValue());
assertEquals("Beef", result.getName());
}
OptionalOrElseVSOrElseGet.orElseBenchmark: [measured 1000000 out of 1000001 rounds, threads: 1 (sequential)]
round: 0.00 [+- 0.00], round.block: 0.00 [+- 0.00], round.gc: 0.00 [+- 0.00], GC.calls: 1, GC.time: 0.05, time.total: 1.35, time.warmup: 0.00, time.bench: 1.35
orElseGetBenchmark
Java Optional orElseGet vs orElse 建立 Optional 容器,取得容器內的值,若值為 Null 則傳回預設值,值如果存在,不會調用 getDefaultValue 方法,執行 100 萬次,效能測試。
@Test
@BenchmarkOptions(benchmarkRounds = 1000000, warmupRounds = 1, concurrency = 1)
public void orElseGetBenchmark() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElseGet(() -> defaultValue());
assertEquals("Beef", result.getName());
}
OptionalOrElseVSOrElseGet.orElseGetBenchmark: [measured 1000000 out of 1000001 rounds, threads: 1 (sequential)]
round: 0.00 [+- 0.00], round.block: 0.00 [+- 0.00], round.gc: 0.00 [+- 0.00], GC.calls: 1, GC.time: 0.05, time.total: 1.26, time.warmup: 0.03, time.bench: 1.23
測試結果
方法 | 耗時 (秒/100w) |
---|---|
orElseBenchmark | 1.35 |
orElseGetBenchmark | 1.23 |
OptionalOrElseVSOrElseGetTest.java
Java Optional orElseGet vs orElse 新增單元測試,驗證是否符合預期。
package org.ruoxue.java_147.optional;
import static org.junit.Assert.*;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
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.Rule;
import org.junit.Test;
import com.carrotsearch.junitbenchmarks.BenchmarkOptions;
import com.carrotsearch.junitbenchmarks.BenchmarkRule;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
public class OptionalOrElseVSOrElseGetTest {
@Rule
public BenchmarkRule benchmarkRule = new BenchmarkRule();
private static SecureRandom secureRandom = null;
public static final String SHA1PRNG = "SHA1PRNG";
public static List<Food> defaultValues = Arrays.asList(new Food("DEFAULT_Beef", 1, 1),
new Food("DEFAULT_Chicken", 2, 1), new Food("DEFAULT_Duck", 3, 1));
static {
new Static();
}
protected static class Static {
public Static() {
try {
secureRandom = SecureRandom.getInstance(SHA1PRNG);
secureRandom.setSeed(System.nanoTime());
} catch (NoSuchAlgorithmException ex) {
ex.printStackTrace();
}
}
}
@NoArgsConstructor
@Getter
@Setter
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();
}
}
public static Food getDefaultValue() {
System.out.println("Call getDefaultValue()");
int index = secureRandom.nextInt(defaultValues.size());
return defaultValues.get(index);
}
@Test
@BenchmarkOptions(benchmarkRounds = 1, warmupRounds = 0, concurrency = 1)
public void orElse() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElse(getDefaultValue());
System.out.println(result);
assertEquals("Beef", result.getName());
}
@Test
@BenchmarkOptions(benchmarkRounds = 1, warmupRounds = 0, concurrency = 1)
public void orElseGet() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElseGet(() -> getDefaultValue());
System.out.println(result);
assertEquals("Beef", result.getName());
}
public static Food defaultValue() {
int index = secureRandom.nextInt(defaultValues.size());
return defaultValues.get(index);
}
@Test
@BenchmarkOptions(benchmarkRounds = 1000000, warmupRounds = 1, concurrency = 1)
public void orElseBenchmark() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElse(defaultValue());
assertEquals("Beef", result.getName());
}
@Test
@BenchmarkOptions(benchmarkRounds = 1000000, warmupRounds = 1, concurrency = 1)
public void orElseGetBenchmark() {
Optional<Food> opt = Optional.ofNullable(new Food("Beef", 1, 1));
Food result = opt.orElseGet(() -> defaultValue());
assertEquals("Beef", result.getName());
}
}
心得分享
Optional orElse vs orElseGet 比較 orElseGet 與 orElse 這兩個方法的執行時間,使用 junit-benchmarks 測試工具,單元測試來驗證產出結果,可以看得出來 orElseGet 比 orElse 方法總耗時比較短, Java Optional orElseGet vs orElse 提供效能測試。