Java14 NullPointerException

Java 14 引入了 NullPointerException 和有用的信息，以防 -XX:+ShowCodeDetailsInExceptionMessages 标志被传递给 JVM。

Java14 NullPointerException的示例

ApiTester.java

package com.yiidian;

public class APITester {
   public static void main(String[] args) {
      String message = null;
      System.out.println(message.length());
   }   
}

旧方法：编译并运行程序

$javac APITester.java
$java APITester

输出结果为

Exception in thread "main" java.lang.NullPointerException
   at APITester.main(APITester.java:6)

新方式：用新标志编译和运行程序

$javac APITester.java
$java -XX:+ShowCodeDetailsInExceptionMessages APITester

输出结果为

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.length()" because "<local1>" is null
   at APITester.main(APITester.java:6)