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Java Convert Array to List - Java 147

Java Convert Array to List – Java 147

Java Convert Array to List

陣列和 List 是最重要的兩種資料結構， Array 是同一資料類型的多個值的集合，可以包含物件和基本類別， List 是屬於 Java Collections 框架的接口，物件的形式有序存儲元素，並保留插入順序，允許存儲重複值，Java Array List 任務是將該 Array 轉換為 List ，本篇增加了範例，並透過單元測試來驗證產出結果。

檔案目錄

./
   +- src
       +- test
       |   +- org
       |       +- ruoxue
       |           +- java_147
       |               +- conversion
       |                   +- array
       |                       +- ArrayToListTest.java

單元測試

Java Array to List 提供陣列轉換成 List 等操作。

iteration

Java Array to List 使用迴圈轉換成 List 。

	@Test
	public void iteration() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = new ArrayList<>();
		for (String e : array) {
			list.add(e);
		}
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		List<Integer> intList = new ArrayList<>();
		for (int e : intArray) {
			intList.add(e);
		}
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = new ArrayList<>();
		for (int e : integerArray) {
			integerList.add(e);
		}
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());
	}
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]
[147, 168, 151, 460, 484]
[147, 168, 151, 460, 484]

Arrays_asList

Java Array to List 使用 Arrays.asList 轉換成 List。

	@Test
	public void Arrays_asList() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Arrays.asList(array);
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		Integer[] boxedArray = IntStream.of(intArray).boxed().toArray(Integer[]::new);
		List<Integer> intList = Arrays.asList(boxedArray);
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = Arrays.asList(integerArray);
		System.out.println(integerList);
		assertEquals(expectedSize, integerList.size());
	}
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]
[147, 168, 151, 460, 484]
[147, 168, 151, 460, 484]

Collections_addAll

Java Array to List 使用 Collections.addAll 轉換成 List。

	@Test
	public void Collections_addAll() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = new ArrayList<>();
		Collections.addAll(list, array);
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		List<Integer> intList = new ArrayList<>();
		Integer[] boxedArray = Arrays.stream(intArray).boxed().toArray(Integer[]::new);
		Collections.addAll(intList, boxedArray);
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = new ArrayList<>();
		Collections.addAll(integerList, integerArray);
		System.out.println(integerList);
		assertEquals(expectedSize, integerList.size());
	}
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]
[147, 168, 151, 460, 484]
[147, 168, 151, 460, 484]

Arrays_stream

Java Array to List 使用 Arrays.stream 轉換成 List。

	@Test
	public void Arrays_stream() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Arrays.stream(array).collect(Collectors.toList());
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		list = Arrays.stream(array).collect(Collectors.toCollection(LinkedList::new));
		System.out.println(list);
		assertEquals(LinkedList.class, list.getClass());
	}
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]

Stream_of

Java Array to List 使用 Stream.of 轉換成 List。

	@Test
	public void Stream_of() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Stream.of(array).collect(Collectors.toList());
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		list = Stream.of(array).collect(Collectors.toCollection(LinkedList::new));
		System.out.println(list);
		assertEquals(LinkedList.class, list.getClass());
	}

[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]
[Java 147, Spring boot 168, Junit 151, Bash 460, IT 484]

ArrayToListTest.java

Convert Array to List in Java 新增單元測試，驗證是否符合預期。

package org.ruoxue.java_147.conversion.array;

import static org.junit.Assert.*;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import org.junit.Test;

public class ArrayToListTest {

	@Test
	public void iteration() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = new ArrayList<>();
		for (String e : array) {
			list.add(e);
		}
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		List<Integer> intList = new ArrayList<>();
		for (int e : intArray) {
			intList.add(e);
		}
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = new ArrayList<>();
		for (int e : integerArray) {
			integerList.add(e);
		}
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());
	}

	@Test
	public void Arrays_asList() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Arrays.asList(array);
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		Integer[] boxedArray = IntStream.of(intArray).boxed().toArray(Integer[]::new);
		List<Integer> intList = Arrays.asList(boxedArray);
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = Arrays.asList(integerArray);
		System.out.println(integerList);
		assertEquals(expectedSize, integerList.size());
	}

	@Test
	public void Collections_addAll() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = new ArrayList<>();
		Collections.addAll(list, array);
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		int[] intArray = { 147, 168, 151, 460, 484 };
		List<Integer> intList = new ArrayList<>();
		Integer[] boxedArray = Arrays.stream(intArray).boxed().toArray(Integer[]::new);
		Collections.addAll(intList, boxedArray);
		System.out.println(intList);
		assertEquals(expectedSize, intList.size());

		Integer[] integerArray = { 147, 168, 151, 460, 484 };
		List<Integer> integerList = new ArrayList<>();
		Collections.addAll(integerList, integerArray);
		System.out.println(integerList);
		assertEquals(expectedSize, integerList.size());
	}

	@Test
	public void Arrays_stream() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Arrays.stream(array).collect(Collectors.toList());
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		list = Arrays.stream(array).collect(Collectors.toCollection(LinkedList::new));
		System.out.println(list);
		assertEquals(LinkedList.class, list.getClass());
	}

	@Test
	public void Stream_of() {
		int expectedSize = 5;
		String[] array = { "Java 147", "Spring boot 168", "Junit 151", "Bash 460", "IT 484" };
		List<String> list = Stream.of(array).collect(Collectors.toList());
		System.out.println(list);
		assertEquals(expectedSize, list.size());

		list = Stream.of(array).collect(Collectors.toCollection(LinkedList::new));
		System.out.println(list);
		assertEquals(LinkedList.class, list.getClass());
	}
}

心得分享

Array to List in Java 可以使用不同的方法將 Array 轉換為 List ， Convert Array to List in Java 提供將 Array 實例轉換為 List 實例的多種方法。

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