这个错误什么情况

这个错误什么情况

package com.andreas.util;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.mchange.v2.c3p0.ComboPooledDataSource;



public class JdbcUtil {

	/*
	 * 创建一个静态常量
	 */
	private static final ComboPooledDataSource datasource = new ComboPooledDataSource();
	/**
	 * 获得连接的方法
	 * @return
	 * @throws SQLException 
	 */
	public static Connection getconnection() throws SQLException {
		Connection  conn = datasource.getConnection();
		return conn;
	}

	/*
	 * 释放资源
	 */
	public static final void re(Statement sta,Connection conn,ResultSet res) {
		if(sta != null) {
			try {
				sta.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}sta = null;
		}
		if(conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}conn = null;
		}
		if(res != null) {
			try {
				res.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}res = null;
		}
	}
}
package com.andreas.demo;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import org.junit.Test;

import com.andreas.util.JdbcUtil;
import com.mchange.v2.c3p0.ComboPooledDataSource;

public class Jdbc_C3p0_Demo {
	@Test
	/*
	 * 手动创建连接池
	 */
	public  void demo1() {
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet res = null;
		//创建连接池
		ComboPooledDataSource cpds = new ComboPooledDataSource();
		try {
			//配置连接池
			cpds.setDriverClass("com.mysql.jdbc.Driver");
			cpds.setJdbcUrl("jdbc:mysql://localhost:3306/jdbc?serverTimezone=Hongkong&useUnicode=true&characterEncoding=utf-8&userSSL=false");
			cpds.setUser("root");
			cpds.setPassword("123456");
			
		//获得连接
		conn  = cpds.getConnection();
		//编写sql
		String sql = "select * from course;";
		//预处理sql
		pstmt = conn.prepareStatement(sql);
		//添加参数
		//执行sql
		res = pstmt.executeQuery();
		while(res.next()) {
			System.out.println(res.getString("id")+"     "+res.getString("name")+"     "+res.getString("category")+"     "+res.getString("desp")+"     "+res.getString("createTime"));
		}
		}catch(Exception e) {
			e.printStackTrace();
		}
		finally {
		//释放资源
			JdbcUtil.re(pstmt, conn, res);
		}
	}
	
	/*
	 * 使用配置文件创建连接池
	 */
	@Test
	public void demo2() {
		Connection conn = null;
		ResultSet res = null;
		PreparedStatement pstmt = null;
		try {
			//获得连接
			conn  = JdbcUtil.getconnection();
			//编写sql
			String sql = "select * from course;";
			//预处理sql
			pstmt = conn.prepareStatement(sql);
			//添加参数
			//执行sql
			res = pstmt.executeQuery();
			while(res.next()) {
				System.out.println(res.getString("id")+"     "+res.getString("name")+"     "+res.getString("category")+"     "+res.getString("desp")+"     "+res.getString("createTime"));
			}
		}catch(Exception e) {
			e.printStackTrace();
		}
		finally {
			JdbcUtil.re(pstmt, conn, res);
		}
	}
}
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>

  <default-config>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
	<property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbc?serverTimezone=Hongkong&useUnicode=true&characterEncoding=utf-8&userSSL=false</property>
	<property name="user">root</property>
	<property name="password">123</property>
	<property name="initialPoolSize">5</property>
	<property name="maxPoolSize">20</property>
  </default-config>
  
</c3p0-config>

demo1运行正常，用了配置文件就会报错，而且会计算很久才会报错

六月 07, 2020 4:46:53 下午 com.mchange.v2.log.MLog <clinit>
信息: MLog clients using java 1.4+ standard logging.
[Fatal Error] :6:94: 对实体 "useUnicode" 的引用必须以 ';' 分隔符结尾。
六月 07, 2020 4:46:53 下午 com.mchange.v2.c3p0.cfg.C3P0Config <clinit>
警告: XML configuration disabled! Verify that standard XML libs are available.
org.xml.sax.SAXParseException; lineNumber: 6; columnNumber: 94; 对实体 "useUnicode" 的引用必须以 ';' 分隔符结尾。
	at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)
	at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)
	at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)
	at com.mchange.v2.c3p0.cfg.C3P0ConfigXmlUtils.extractXmlConfigFromInputStream(C3P0ConfigXmlUtils.java:136)
	at com.mchange.v2.c3p0.cfg.C3P0ConfigXmlUtils.extractXmlConfigFromDefaultResource(C3P0ConfigXmlUtils.java:119)
	at com.mchange.v2.c3p0.cfg.DefaultC3P0ConfigFinder.findConfig(DefaultC3P0ConfigFinder.java:49)
	at com.mchange.v2.c3p0.cfg.C3P0Config.<clinit>(C3P0Config.java:92)
	at com.mchange.v2.c3p0.impl.PoolBackedDataSourceBase.<init>(PoolBackedDataSourceBase.java:46)
	at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.<init>(AbstractPoolBackedDataSource.java:62)
	at com.mchange.v2.c3p0.ComboPooledDataSource.<init>(ComboPooledDataSource.java:109)
	at com.mchange.v2.c3p0.ComboPooledDataSource.<init>(ComboPooledDataSource.java:105)
	at com.andreas.demo.Jdbc_C3p0_Demo.demo1(Jdbc_C3p0_Demo.java:22)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)

六月 07, 2020 4:46:53 下午 com.mchange.v2.c3p0.C3P0Registry banner
信息: Initializing c3p0-0.9.1.2 [built 21-May-2007 15:04:56; debug? true; trace: 10]
六月 07, 2020 4:46:54 下午 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 2sbfa7aa13e0edb1j6pf68|3b764bce, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 2sbfa7aa13e0edb1j6pf68|3b764bce, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql://localhost:3306/jdbc?serverTimezone=Hongkong&useUnicode=true&characterEncoding=utf-8&userSSL=false, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
18     Java语法     java      java基础语法     2020-06-06 00:00:00
20     前端小白     前端      HTML/CSS/JS     2020-06-06 00:00:00
21     Java语法     java      java基础语法     2020-06-06 00:00:00
23     前端小白     前端      HTML/CSS/JS     2020-06-06 00:00:00
六月 07, 2020 4:46:54 下午 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 2sbfa7aa13e0edb1j6pf68|7a79be86, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> null, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 2sbfa7aa13e0edb1j6pf68|7a79be86, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> null, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
六月 07, 2020 4:47:23 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@f68838f -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.sql.SQLException: No suitable driver
	at java.sql.DriverManager.getDriver(Unknown Source)
	at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:223)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:119)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:143)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:132)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

六月 07, 2020 4:47:23 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2b47cd59 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.sql.SQLException: No suitable driver
	at java.sql.DriverManager.getDriver(Unknown Source)
	at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:223)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:119)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:143)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:132)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

六月 07, 2020 4:47:23 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@21bf02b8 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.sql.SQLException: No suitable driver
	at java.sql.DriverManager.getDriver(Unknown Source)
	at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:223)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:119)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:143)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:132)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

java.sql.SQLException: Connections could not be acquired from the underlying database!
	at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
	at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
	at com.andreas.util.JdbcUtil.getconnection(JdbcUtil.java:24)
	at com.andreas.demo.Jdbc_C3p0_Demo.demo2(Jdbc_C3p0_Demo.java:61)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
	at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
	at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
	at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
	... 26 more
孬帮手慕小菜 2020-06-07
源自：JDBC入门   7-4 自由编程
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2回答
好帮手慕小脸 2020-06-09 16:59:03

同学你好，测试同学的代码是正确的且可以正常运行，如下所示：

http://img1.sycdn.imooc.com//climg/5edf4dda09e0244e08780427.jpg

问一下同学还是出现上述这个错误吗？如果是，同学是否导入了mysql的jar包，mysql的jar包版本是否和自己安装的版本一致。建议同学检查一下。

祝学习愉快~

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好帮手慕小脸 2020-06-07 17:40:28

同学你好，报错提示没有合适的Driver，如：

http://img1.sycdn.imooc.com//climg/5edcb49e094ac47905380138.jpg

这里是因为同学数据库连接的地址书写有误，在xml中要写成&amp;

如果我的回答解决了你的疑惑，请采纳！祝学习愉快！

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  • 提问者 孬帮手慕小菜 #1
    请老师解释一下呗
    2020-06-07 18:34:34
  • 好帮手慕小脸 回复 提问者 孬帮手慕小菜 #2
    同学你好，这里是需要解释&amp;吗？如果是，是因为xml中不允许出现&,<,>等特殊字符，所以XML中需要将 "&"转义"&amp;" 如果我的回答解决了你的疑惑，请采纳！祝学习愉快！
    2020-06-07 18:39:04
  • 提问者 孬帮手慕小菜 回复 好帮手慕小脸 #3
    <?xml version="1.0" encoding="UTF-8"?> <c3p0-config> <default-config> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbc?serverTimezone=Hongkong&amp;useUnicode=true&amp; characterEncoding=utf-8&amp;userSSL=false</property> <property name="user">root</property> <property name="password">123</property> <property name="initialPoolSize">5</property> <property name="maxPoolSize">20</property> </default-config> </c3p0-config> 这样写还是报错啊
    2020-06-09 16:42:47
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3. Java 数据库开发与实战应用
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本阶段将带你学习MySQL数据库，JDBC接口，MyBatis框架等，带你掌握的数据的存放和管理。

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在ldea如何创建和eclipse中Dynamic Web project 一样的

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对于集合来说，能不能通过索引（数字）的方式同时插入多个字符？

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老师，在集合类中我取值3，为什么结果显示是A,B，而不是C呢

22 3

centos下载问题

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新的学员可以来看一下，我总结的截止到现在遇到的安装问题

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