java49的简单介绍

admin 2023-03-20 15:16:10 498

本篇文章给大家谈谈java49，以及对应的知识点，希望对各位有所帮助，不要忘了收藏本站喔。

本文目录一览：

1、java中 char = 49; 这里的49是什么类型的？
2、java中49能用单引号括着，用System.out.println('49')输出吗?
3、java 如何输入字符。自己写了一个但输入1后出现49，求解答。
4、java错误: 找不到符号？
5、java中提示找不到的符号
6、jedis连接集群报Could not get a resource from the pool错误

java中 char = 49; 这里的49是什么类型的？

char直接赋数字的话，就是赋值为该数字ASCII码的对应字符，比如说 char a＝35

等价于:char a＝'#'

java中49能用单引号括着，用System.out.println('49')输出吗?

不可以，‘49’就是个语法错误。‘’是表示字符(char)的，""才是表示字符串的

java 如何输入字符。自己写了一个但输入1后出现49，求解答。

没转型，你输入的1，接受的应该是char类型'1'，输出是int，所以java自动输出了‘1’的unicode码，就是49。用Integer和String的静态方法转型就行了。

Integer.valueOf(String.valueOf('1'));

先把char转成String，在转成int

java错误: 找不到符号？

变量名和方法名错误啊，Truck类里没有getTotal变量和Weights()方法啊，只有getTotalWeights()方法，你把truck.getTotal-Weights() 换成truckTotalWeights()即可

java中提示找不到的符号

class Toy

{

public Toy(int id,String name,float price)

{

int toyId;

String toyName;

float toyPrice;

toyId=id;

toyName=name;

toyPrice=price;

System.out.println(toyId);

System.out.println(toyName);

System.out.println(price);

}

/*class Customer

{

int custId;

String custName;

String custAddress;

float Amt_outstanding;

public Customer(int id,String name,String address)

{

custId=id;

custName=name;

custAddress=address;

System.out.println(custId);

System.out.println(custName);

System.out.println(custAddress);

}

class OnlineCustomer extends Customer

{

public OnlineCustomer(int cId,String name,String address,String id,String cardno)

{

String loginId;

String masterCardNo;

loginId=id;

masterCardNo=cardno;

System.out.println(loginId);

System.out.println(masterCardNo);

super.Customer(cId,name,address);

}

} */

class Test

{

public static void main(String aa[])

{

Toy obj1= new Toy(001,"Barbie Doll",40); //如果你要输入T001的话id就要设置为String

}

///////////////////////////////////////////

//////////好了Toy类没错了/.////////////

class Toy

{

public Toy(int id,String name,float price)

{

int toyId;

String toyName;

float toyPrice;

toyId=id;

toyName=name;

toyPrice=price;

System.out.println(toyId);

System.out.println(toyName);

System.out.println(price);

}

class Customer

{

int custId;

String custName;

String custAddress;

float Amt_outstanding;

public Customer(int id,String name,String address)

{

custId=id;

custName=name;

custAddress=address;

System.out.println(custId);

System.out.println(custName);

System.out.println(custAddress);

}

/*class OnlineCustomer extends Customer

{

public OnlineCustomer(int cId,String name,String address,String id,String cardno)

{

String loginId;

String masterCardNo;

loginId=id;

masterCardNo=cardno;

System.out.println(loginId);

System.out.println(masterCardNo);

super.Customer(cId,name,address);

}

} */

class Test

{

public static void main(String aa[])

{

Toy obj1= new Toy(001,"Barbie Doll",40); //如果你要输入T001的话id就要设置为String

Customer cs=new Customer(001,"beijin","北京"); //证明你的Customer 类没有错！

//OnlineCustomer obj2 = new OnlineCustomer();

//obj2.super.OnlineCustomer("C001","Carol","164, Redmond Way, Ohio","carol@pixelfairiesnet","9473884833");

}

/////////////////////////////////

/////////Customer 类也没错///////

/////////////////////////////

接下来的问题你就自己解决拉!!!简单

jedis连接集群报Could not get a resource from the pool错误

Caused by: org.springframework.data.redis.RedisConnectionFailureException: Could not get a resource from the pool; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool

at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:67)

at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:41)

at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:37)

at org.springframework.data.redis.connection.jedis.JedisClusterConnection.convertJedisAccessException(JedisClusterConnection.java:3999)

at org.springframework.data.redis.connection.jedis.JedisClusterConnection.setEx(JedisClusterConnection.java:717)

at org.springframework.data.redis.core.DefaultValueOperations 11.doInRedis(DefaultValueOperations.java:186)

at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:207)

at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:169)

at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:91)

at org.springframework.data.redis.core.DefaultValueOperations.set(DefaultValueOperations.java:182)

at io.renren.common.utils.SuppleDataUtils.provideIcc(SuppleDataUtils.java:107)

at io.renren.modules.job.task.TaskIcc.taskFour(TaskIcc.java:242)

... 10 common frames omitted

Caused by: redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool

at redis.clients.util.Pool.getResource(Pool.java:53)

at redis.clients.jedis.JedisPool.getResource(JedisPool.java:226)

at redis.clients.jedis.JedisSlotBasedConnectionHandler.getConnectionFromSlot(JedisSlotBasedConnectionHandler.java:66)

at redis.clients.jedis.JedisClusterCommand.runWithRetries(JedisClusterCommand.java:116)

at redis.clients.jedis.JedisClusterCommand.runWithRetries(JedisClusterCommand.java:141)

at redis.clients.jedis.JedisClusterCommand.runBinary(JedisClusterCommand.java:60)

at redis.clients.jedis.BinaryJedisCluster.setex(BinaryJedisCluster.java:268)

at org.springframework.data.redis.connection.jedis.JedisClusterConnection.setEx(JedisClusterConnection.java:715)

... 18 common frames omitted

Caused by: redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketTimeoutException: connect timed out

at redis.clients.jedis.Connection.connect(Connection.java:207)

at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:93)

at redis.clients.jedis.BinaryJedis.connect(BinaryJedis.java:1767)

at redis.clients.jedis.JedisFactory.makeObject(JedisFactory.java:106)

at org.apache.commons.pool2.impl.GenericObjectPool.create(GenericObjectPool.java:868)

at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:435)

at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:363)

at redis.clients.util.Pool.getResource(Pool.java:49)

... 28 common frames omitted

Caused by: java.net.SocketTimeoutException: connect timed out

at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)

at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)

at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)

at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)

at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)

at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)

at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)

at java.net.Socket.connect(Socket.java:589)

at redis.clients.jedis.Connection.connect(Connection.java:184)

... 35 common frames omitted

最近在本地测试通过springboot基础redis的方式连接redis集群，启动的时候没有报错。

到时当执行保存，查询到redis的操作的时候，报上面的错误。

首先看到错误信息，先是connect timed out后，再出现的Could not get a resource from the pool错误。一开始排查这个错误，由于使用的是默认连接池，debug的时候，也看到有装载连接池，为啥报错呢。本地通过redis-manger工具，连接集群地址也可以连接访问。从日志也看不出还有其他的错误信息。

于是自己写了main方法直接操作JedisCluster的方式来测试，出现的错误跟上面全文一样。用抓包工具wireshark过滤集群的地址，查看连接的消息也是正常的。

另外一个项目使用的reddison客户端，于是测试了deamo用reddison来连接集群地址，启动的时候，发现报如下错误

乖乖，恍然大悟；10.287.17.31地址是服务器的内网地址，本机是连不上内网地址的，只有通过外网地址连接。而我配置的是外网地址。然而，客户端在集群同步和心跳检查的时候，是拉取的集群信息，redis集群信息里面的节点的信息

配置的是内网地址。客户端就通过这个内网地址来同步信息了。

再次同wireshark过滤集群10.287.17.31，发现有大量的超时重传的包，也没有响应。

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