异常信息：java.lang.ExceptionInInitializerError

代码

public enum KafkaSetting {

    CONSUMER,
    PRIVATER;

    KafkaSetting() {
        initProperties(this);
    }

    public Properties prop = new Properties();

   // 这里设置一些属性
    private void initProperties(KafkaSetting  s) {
        switch (s) {
            case CONSUMER:
                prop.put(ConsumerConfig.GROUP_ID_CONFIG,"G1");
                break;
            case PRIVATER:
                prop.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.44.128:9092");
                break;
            default:
                throw new IllegalArgumentException("Unknown type:" + this.getClass().getName());
        }

    }

}

测试Demo

@Test
    public void kafkaSetting_test() {
        KafkaSetting consumer = KafkaSetting.CONSUMER;
        Properties prop = consumer.prop;
        System.out.println(prop.size());
    }

错误信息

java.lang.ExceptionInInitializerError
    at com.xiaoxiong.utils.KafkaSetting.initProperties(KafkaSetting.java:27)
    at com.xiaoxiong.utils.KafkaSetting.<init>(KafkaSetting.java:21)
    at com.xiaoxiong.utils.KafkaSetting.<clinit>(KafkaSetting.java:17)
    at com.xiaoxiong.utils.KafkaSettingTest.kafkaSetting_test(KafkaSettingTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
    at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
    at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.lang.NullPointerException
    at com.xiaoxiong.utils.KafkaSetting.values(KafkaSetting.java:15)
    at com.xiaoxiong.utils.KafkaSetting$1.<clinit>(KafkaSetting.java:27)
    ... 29 more

空指针错误了

构造方法前加public

兄弟，你对枚举类理解有错误

根据你目前的写法，我知道你是想把

case CONSUMER:
                prop.put(ConsumerConfig.GROUP_ID_CONFIG,"G1");
                break;
            case PRIVATER:
                prop.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.44.128:9092");
                break;

这两个都存进同一个Properties中，但是你这个写法是不可以的，主要错在三点：
第一，枚举初始化时机更早，比类成员变量的初始化还要早，所以public Properties prop的初始化应该写在构造方法里
第二，不能用switch，应该用forEach遍历values数组
第三，及时你按照第一、第二问题改了，你会发现，会存在两个Properties，分别归属于CONSUMER和PRIVATER的各一个，应该把public Properties prop写成静态的，才可

这有个曲线救国的方案:

public enum KafkaSetting {

    CONSUMER("CONSUMER"),
    PRIVATER("PRIVATER");

    private String name;

    KafkaSetting(String name) {
        this.name = name;
        initProperties(name);
    }

    public Properties prop = new Properties();

    // 这里设置一些属性
    private void initProperties(String s) {
        switch (s) {
            case "CONSUMER":
                prop.put(ConsumerConfig.GROUP_ID_CONFIG,"G1");
                break;
            case "PRIVATER":
                prop.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.44.128:9092");
                break;
            default:
                throw new IllegalArgumentException("Unknown type:" + this.getClass().getName());
        }

    }

    public static void main(String[] args) {
        KafkaSetting consumer = KafkaSetting.PRIVATER;
        Properties prop = consumer.prop;
        System.out.println(prop);

    }
}