Java Convert Char to String – Java 147

Post author:若雪
Post published:2023-03-11
Post category:RD / Java / Java Conversion / Java Conversion String
Post comments:0 Comments
Post last modified:2023-11-07

Table of Contents

Java Convert Char to String

提供將 char 轉換為 String，字元轉換為字串的方法，可以使用 toString 、 valueOf 等方法進行操作， Java Char String 任務是將該字元轉換為字串，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
       |                   +- string
       |                       +- CharToStringTest.java

單元測試

Java Char to String 提供字元轉換成字串等操作。

toStringz

Java Char to String 使用 Character.toString 轉換成字串。

	@Test
	public void toStringz() {
		char value = 'g';
		String result = Character.toString(value);
		System.out.println(result);
		assertEquals("g", result);

		value = '1';
		result = Character.toString(value);
		System.out.println(result);
		assertEquals("1", result);
	}

g
1

character

Java Char to String 使用 Character 建構子，傳入參數字元，建立一個新的 Character 物件，再使用 toString 轉換成字串。

	@Test
	public void character() {
		Character value = new Character('g');
		String result = value.toString();
		System.out.println(result);
		assertEquals("g", result);

		value = new Character('1');
		result = value.toString();
		System.out.println(result);
		assertEquals("1", result);
	}

g
1

valueOf

Java Char to String 使用 String.valueOf 轉換成字串。

	@Test
	public void valueOf() {
		char value = 'g';
		String result = String.valueOf(value);
		System.out.println(result);
		assertEquals("g", result);

		char[] array = new char[] { 'g', 'r', 'a', 'd', 'l', 'e' };
		result = String.valueOf(array);
		System.out.println(result);
		assertEquals("gradle", result);

		result = String.valueOf(array, 1, 3);
		System.out.println(result);
		assertEquals("rad", result);
	}

g
gradle
rad

valueOfThrowException

Java Char to String 使用 String.valueOf 轉換成字串，傳入空字元陣列，會拋出例外。

	@Test(expected = NullPointerException.class)
	public void valueOfThrowException() {
		char value = 'g';
		String result = String.valueOf(value);
		System.out.println(result);
		assertEquals("g", result);

		char[] array = null;
		result = String.valueOf(array);
		System.out.println(result);
	}

g
java.lang.NullPointerException
	at java.lang.String.<init>(String.java:166)
	at java.lang.String.valueOf(String.java:3008)
	at org.ruoxue.java_147.conversion.CharToStringTest.valueOfThrowException(CharToStringTest.java:60)

CharToStringTest.java

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

package org.ruoxue.java_147.conversion.string;

import static org.junit.Assert.*;

import org.junit.Test;

public class CharToStringTest {

	@Test
	public void toStringz() {
		char value = 'g';
		String result = Character.toString(value);
		System.out.println(result);
		assertEquals("g", result);

		value = '1';
		result = Character.toString(value);
		System.out.println(result);
		assertEquals("1", result);
	}

	@Test
	public void character() {
		Character value = new Character('g');
		String result = value.toString();
		System.out.println(result);
		assertEquals("g", result);

		value = new Character('1');
		result = value.toString();
		System.out.println(result);
		assertEquals("1", result);
	}

	@Test
	public void valueOf() {
		char value = 'g';
		String result = String.valueOf(value);
		System.out.println(result);
		assertEquals("g", result);

		char[] array = new char[] { 'g', 'r', 'a', 'd', 'l', 'e' };
		result = String.valueOf(array);
		System.out.println(result);
		assertEquals("gradle", result);

		result = String.valueOf(array, 1, 3);
		System.out.println(result);
		assertEquals("rad", result);
	}

	@Test
	public void valueOfThrowException() {
		char value = 'g';
		String result = String.valueOf(value);
		System.out.println(result);
		assertEquals("g", result);

		char[] array = null;
		result = String.valueOf(array);
		System.out.println(result);
	}
}