学习使用String.isBlank()方法确定给定的字符串是空白还是空或仅包含空格。 isBlank()方法已添加到Java 11中。
要检查给定的字符串甚至没有空格，请使用String.isEmpty()方法。
isBlank()方法
如果给定的字符串为空或仅包含空格代码点，则此方法返回 true ，否则返回 false 。
它使用 Character.isWhitespace(char) 方法来确定空白字符。
/** * returns - true if the string is empty or contains only white space codepoints * - otherwise false */public boolean isBlank()
isBlank()示例
检查给定字符串是否为空的Java程序。
public class Main
{
public static void main(String[] args)
{
System.out.println( "ABC".isBlank() ); //false
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln"> </span><span class="str">" ABC "</span><span class="pun">.</span><span class="pln">isBlank</span><span class="pun">()</span><span class="pln"> </span><span class="pun">);</span><span class="pln"> </span><span class="com">//false</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln"> </span><span class="str">" "</span><span class="pun">.</span><span class="pln">isBlank</span><span class="pun">()</span><span class="pln"> </span><span class="pun">);</span><span class="pln"> </span><span class="com">//true</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln"> </span><span class="str">""</span><span class="pun">.</span><span class="pln">isBlank</span><span class="pun">()</span><span class="pln"> </span><span class="pun">);</span><span class="pln"> </span><span class="com">//true</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
}
程序输出。
false false true true
isBlank()与isEmpty()
两种方法都用于检查Java中的空白或空字符串。两种方法之间的区别在于，当且仅当字符串长度为0时， isEmpty()方法返回 true 。
isBlank()方法仅检查非空白字符。它不检查字符串长度。
public class Main
{
public static void main(String[] args)
{
System.out.println( "ABC".isBlank() ); //false
System.out.println( " ".isBlank() ); //true
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln"> </span><span class="str">"ABC"</span><span class="pun">.</span><span class="pln">isEmpty</span><span class="pun">()</span><span class="pln"> </span><span class="pun">);</span><span class="pln"> </span><span class="com">//false</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln"> </span><span class="str">" "</span><span class="pun">.</span><span class="pln">isEmpty</span><span class="pun">()</span><span class="pln"> </span><span class="pun">);</span><span class="pln"> </span><span class="com">//false</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
}
程序输出。
false true false false
