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Java Convert String to Short

對包含 short 的字串進行數學運算時，通常會使用轉換成 short ，從文本字段或文本區域讀取資料時，輸入的資料都會作為字串接收，將字串轉換為 short ，可以使用 parseShort 、 valueOf 等方法進行操作， Java String Short 任務是將該字串轉換為短整數，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
       |                       +- StringToShortTest.java

單元測試

Java String to Short 提供字串轉換成短整數等操作。

parseShort

Java String to Short 使用 Short.parseShort 轉換成短整數，此方法接受另一個參數來更改基數，例如 16（十六進制）或 2（二進制）。

	@Test
	public void parseShort() {
		String value = "155";
		short result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(155, result);

		value = "-70";
		result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(-70, result);

		value = "70";
		// (7)*16^1 + (0)*16^0 = 112
		// 96 + 0 = 112
		result = Short.parseShort(value, 16);
		System.out.println(result);
		assertEquals(112, result);

		value = "111111";
		// (1)*2^5 + (1)*2^4 + (1)*2^3 + (1)*2^2 + (1)*2^1 + (1)*2^0 = 63
		// 32 + 16 + 8 + 4 + 2 + 1= 63
		result = Short.parseShort(value, 2);
		System.out.println(result);
		assertEquals(63, result);
	}

parseShortThrowException

Java String to Short 使用 Short.parseShort 轉換成短整數，輸入不合格式的字串，會拋出例外。

	@Test(expected = NumberFormatException.class)
	public void parseShortThrowException() {
		String value = "155";
		short result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(155, result);

		value = "assertj-155";
		result = Short.parseShort(value);
		System.out.println(result);
	}

155
java.lang.NumberFormatException: For input string: "assertj-155"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Integer.parseInt(Integer.java:580)
	at java.lang.Short.parseShort(Short.java:118)
	at java.lang.Short.parseShort(Short.java:144)
	at org.ruoxue.java_147.string.StringToShortTest.parseShortThrowException(StringToShortTest.java:44)

valueOf

Java String to Short 使用 Short.valueOf 轉換成短整數。

	@Test
	public void valueOf() {
		String value = "155";
		Short result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(155, result.shortValue());

		value = "-70";
		result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(-70, result.shortValue());

		value = "70";
		// (7)*16^1 + (0)*16^0 = 112
		result = Short.valueOf(value, 16);
		System.out.println(result);
		assertEquals(112, result.shortValue());

		value = "111111";
		// (1)*2^5 + (1)*2^4 + (1)*2^3 + (1)*2^2 + (1)*2^1 + (1)*2^0 = 63
		// 32 + 16 + 8 + 4 + 2 + 1= 63
		result = Short.valueOf(value, 2);
		System.out.println(result);
		assertEquals(63, result.shortValue());
	}

valueOfThrowException

Convert String to Short in Java 使用 Short.valueOf 轉換成短整數，輸入不合格式的字串，會拋出例外。

	@Test(expected = NumberFormatException.class)
	public void valueOfThrowException() {
		String value = "155";
		Short result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(155, result.shortValue());

		value = "assertj-155";
		result = Short.valueOf(value);
		System.out.println(result);
	}

155
java.lang.NumberFormatException: For input string: "assertj-155"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Integer.parseInt(Integer.java:580)
	at java.lang.Short.parseShort(Short.java:118)
	at java.lang.Short.valueOf(Short.java:174)
	at java.lang.Short.valueOf(Short.java:200)
	at org.ruoxue.java_147.string.StringToShortTest.valueOfThrowException(StringToShortTest.java:82)

StringToShortTest.java

Convert String to Short 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 StringToShortTest {

	@Test
	public void parseShort() {
		String value = "155";
		short result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(155, result);

		value = "-70";
		result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(-70, result);

		value = "70";
		// (7)*16^1 + (0)*16^0 = 112
		// 96 + 0 = 112
		result = Short.parseShort(value, 16);
		System.out.println(result);
		assertEquals(112, result);

		value = "111111";
		// (1)*2^5 + (1)*2^4 + (1)*2^3 + (1)*2^2 + (1)*2^1 + (1)*2^0 = 63
		// 32 + 16 + 8 + 4 + 2 + 1= 63
		result = Short.parseShort(value, 2);
		System.out.println(result);
		assertEquals(63, result);
	}

	@Test(expected = NumberFormatException.class)
	public void parseShortThrowException() {
		String value = "155";
		short result = Short.parseShort(value);
		System.out.println(result);
		assertEquals(155, result);

		value = "assertj-155";
		result = Short.parseShort(value);
		System.out.println(result);
	}

	@Test
	public void valueOf() {
		String value = "155";
		Short result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(155, result.shortValue());

		value = "-70";
		result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(-70, result.shortValue());

		value = "70";
		// (7)*16^1 + (0)*16^0 = 112
		result = Short.valueOf(value, 16);
		System.out.println(result);
		assertEquals(112, result.shortValue());

		value = "111111";
		// (1)*2^5 + (1)*2^4 + (1)*2^3 + (1)*2^2 + (1)*2^1 + (1)*2^0 = 63
		// 32 + 16 + 8 + 4 + 2 + 1= 63
		result = Short.valueOf(value, 2);
		System.out.println(result);
		assertEquals(63, result.shortValue());
	}

	@Test(expected = NumberFormatException.class)
	public void valueOfThrowException() {
		String value = "155";
		Short result = Short.valueOf(value);
		System.out.println(result);
		assertEquals(155, result.shortValue());

		value = "assertj-155";
		result = Short.valueOf(value);
		System.out.println(result);
	}
}

心得分享

String to Short in Java 轉換方法 parseShort 和 valueOf 似乎完全相同，分別傳回基本型別 short 及物件 Short ， valueOf 方法在內部委託給 parseShort 方法，這兩種方法之間存在一個細微差別： valueOf 方法在內部使用整數快取，快取將為 -128 和 127 之間的數字返回相同的 Short 實例，建議使用 valueOf 而不是 parseShort 來取得物件 Short ，因為快取可以為系統提高效率， Convert String to Short in Java 提供將 String 實例轉換為 short 或 Short 實例的多種方法。