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                # Java `String isEmpty()`方法 > 原文: [https://beginnersbook.com/2017/10/java-string-isempty-method-with-example/](https://beginnersbook.com/2017/10/java-string-isempty-method-with-example/) Java `String isEmpty()`方法檢查`String`是否為空。如果給定的字符串為空,則此方法返回`true`,否則返回`false`。換句話說,如果字符串的[長度](https://beginnersbook.com/2013/12/java-string-length-method-example/)為 0,則可以說此方法返回`true`。 `isEmpty()`方法的簽名:** ```java public boolean isEmpty() ``` ## Java `String isEmpty()`方法示例 ```java public class Example{ public static void main(String args[]){ //empty string String str1=""; //non-empty string String str2="hello"; //prints true System.out.println(str1.isEmpty()); //prints false System.out.println(str2.isEmpty()); } } ``` 輸出: ```java true false ``` ## Java `String isEmpty()`方法檢查字符串是否為空或空的示例 正如我們在上面的例子中看到的那樣,`isEmpty()`方法只檢查`String`是否為空。如果要檢查`String`是否為`null`或為空,則可以執行此操作,如以下示例所示。 ```java public class Example{ public static void main(String args[]){ String str1 = null; String str2 = "beginnersbook"; if(str1 == null || str1.isEmpty()){ System.out.println("String str1 is empty or null"); } else{ System.out.println(str1); } if(str2 == null || str2.isEmpty()){ System.out.println("String str2 is empty or null"); } else{ System.out.println(str2); } } } ``` 輸出: ```java String str1 is empty or null beginnersbook ``` #### 參考 [`String isEmpty()`方法 - JavaDoc](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#isEmpty()) #### 相關文章 1. [Java `String intern()`方法](https://beginnersbook.com/2017/10/java-string-intern-method/) 2. [Java `String format()`方法](https://beginnersbook.com/2017/10/java-string-format-method/) 3. [Java `String substring()`](https://beginnersbook.com/2013/12/java-string-substring-method-example/) 4. [Java 8 - `StringJoiner`示例](https://beginnersbook.com/2017/10/java-8-stringjoiner/)
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