Table of Contents

Initialize String in Java

一般而言有幾種字串初始化的方法，除了使用文字或 new 關鍵字建立字串之外，String 也提供了 int[] 、 StringBuffer 、 StringBuilder 等建構子來建立字串， Initialize String Java 介紹了初始化字串等操作，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
       |               +- string
       |                   +- InitializeStringTest.java

單元測試

Java Initialize String 提供初始化建立字串。

withIntArray

使用 int 陣列，建立一個 String 。

	@Test
	public void withIntArray() {
		int[] value = new int[] { 65, 115, 115, 101, 114, 116, 106 };
		String result = new String(value, 0, value.length);
		System.out.println(result);
		assertEquals("Assertj", result);

		int[] value2 = new int[] { 65, 115, 115, 101, 114, 116, 106, 32, 49, 53, 53 };
		String result2 = new String(value2, 8, 3);
		System.out.println(result2);
		assertEquals("155", result2);
	}

Assertj
155

withString

Java Initialize String 使用另一個字串，建立一個 String 。

	@Test
	public void withString() {
		String value = "Assertj";
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		String value2 = "155";
		String result2 = new String(value2);
		System.out.println(result2);
		assertEquals("155", result2);
	}

Assertj
155

withStringBuffer

Java Initialize String 使用 StringBuffer ，建立一個 String 。

	@Test
	public void withStringBuffer() {
		StringBuffer value = new StringBuffer("Assertj");
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		value.append(" 155");
		String result2 = new String(value);
		System.out.println(result2);
		assertEquals("Assertj 155", result2);
	}

Assertj
Assertj 155

withStringBuilder

Java Initialize String 使用 StringBuilder ，建立一個 String 。

	@Test
	public void withStringBuilder() {
		StringBuilder value = new StringBuilder("Assertj");
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		value.append(" 155");
		String result2 = new String(value);
		System.out.println(result2);
		assertEquals("Assertj 155", result2);
	}

Assertj
Assertj 155

InitializeStringTest.java

String Initialization Java 新增單元測試，驗證是否符合預期。

package org.ruoxue.java_147.string;

import static org.junit.Assert.*;

import org.junit.Test;

public class InitializeStringTest {

	@Test
	public void withIntArray() {
		int[] value = new int[] { 65, 115, 115, 101, 114, 116, 106 };
		String result = new String(value, 0, value.length);
		System.out.println(result);
		assertEquals("Assertj", result);

		int[] value2 = new int[] { 65, 115, 115, 101, 114, 116, 106, 32, 49, 53, 53 };
		String result2 = new String(value2, 8, 3);
		System.out.println(result2);
		assertEquals("155", result2);
	}

	@Test
	public void withString() {
		String value = "Assertj";
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		String value2 = "155";
		String result2 = new String(value2);
		System.out.println(result2);
		assertEquals("155", result2);
	}

	@Test
	public void withStringBuffer() {
		StringBuffer value = new StringBuffer("Assertj");
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		value.append(" 155");
		String result2 = new String(value);
		System.out.println(result2);
		assertEquals("Assertj 155", result2);
	}

	@Test
	public void withStringBuilder() {
		StringBuilder value = new StringBuilder("Assertj");
		String result = new String(value);
		System.out.println(result);
		assertEquals("Assertj", result);

		value.append(" 155");
		String result2 = new String(value);
		System.out.println(result2);
		assertEquals("Assertj 155", result2);
	}
}