Question

为什么我的回文程序不能正常工作？始终会返回false，我无法说明原因。

这是我的代码：

public static boolean isPalindromIterative(String string) {
    int a = 0;
    int b = string.length() - 1;        
    while (b > a) {
        if (a != b) {            
            return false;
        }
        a++;
        b--;        
    }
    return true;
}

Answer 1

您正在比较a和b的值，这些值在您开始比较时不相同，因此您的方法会出错。

在if条件下，将其更改为string.charAt(a) != string.chatAt(b)

Answer 2

当你说

时

while (b > a) {
    if (a != b) {

很明显，a不等于b（或者不会输入循环）。按照上下文，我相信你想比较String中的字符。我会使用String.toCharArray()获取char[]并执行类似

的操作

char[] chars = string.toCharArray();
while (b > a) {
    if (chars[a] != chars[b]) {

Answer 3

如果您的代码b > a中有while (b > a)，则代码a中的b不等于if (a != b)。

Answer 4

要在java中检查给定的字符串是否是回文，只需使用reverse()类public static boolean isPalindromIterativeStringBuilder(String string) { StringBuilder sb = new StringBuilder(string); sb.reverse(); //Reverse to the given string return sb.toString().equalsIgnoreCase(string); //Check whether given string is equal to reverse string or not }方法并检查给定的字符串。

SEVERE: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Cannot create inner bean 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' of type [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter] while setting bean property 'jpaVendorAdapter'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:282)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:121)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1393)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1134)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:522)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1117)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:922)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:724)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1013)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:959)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:490)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:271)
    ... 24 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:87)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1006)
    ... 28 more
Caused by: java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:270)
    at org.jboss.logging.Logger$1.run(Logger.java:2252)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.jboss.logging.Logger.getMessageLogger(Logger.java:2227)
    at org.jboss.logging.Logger.getMessageLogger(Logger.java:2214)
    at org.hibernate.jpa.internal.HEMLogging.messageLogger(HEMLogging.java:45)
    at org.hibernate.jpa.internal.HEMLogging.messageLogger(HEMLogging.java:41)
    at org.hibernate.ejb.HibernatePersistence.<clinit>(HibernatePersistence.java:46)
    at org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter.<init>(HibernateJpaVendorAdapter.java:57)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:148)
    ... 30 more
Caused by: java.lang.ClassNotFoundException: org.hibernate.engine.jndi.JndiException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
    ... 45 more

十一月 23, 2015 1:23:18 下午 org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Cannot create inner bean 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' of type [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter] while setting bean property 'jpaVendorAdapter'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:282)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:121)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1393)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1134)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:522)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1117)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:922)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:724)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter#7b0aa31f' defined in ServletContext resource [/WEB-INF/hibernateContext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1013)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:959)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:490)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:271)
    ... 24 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:87)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1006)
    ... 28 more
Caused by: java.lang.NoClassDefFoundError: org/hibernate/engine/jndi/JndiException
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:270)
    at org.jboss.logging.Logger$1.run(Logger.java:2252)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.jboss.logging.Logger.getMessageLogger(Logger.java:2227)
    at org.jboss.logging.Logger.getMessageLogger(Logger.java:2214)
    at org.hibernate.jpa.internal.HEMLogging.messageLogger(HEMLogging.java:45)
    at org.hibernate.jpa.internal.HEMLogging.messageLogger(HEMLogging.java:41)
    at org.hibernate.ejb.HibernatePersistence.<clinit>(HibernatePersistence.java:46)
    at org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter.<init>(HibernateJpaVendorAdapter.java:57)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:148)
    ... 30 more
Caused by: java.lang.ClassNotFoundException: org.hibernate.engine.jndi.JndiException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
    ... 45 more

Answer 5

这也是一种迭代方法。如果我帮助了某人，我会很高兴。 ;)

public static boolean isPalindromeIterative(String string) {
String polindromCheck = string.toUpperCase();
for (int index = 0; index < polindromCheck.length(); index++) {
  if (polindromCheck.charAt(index) != polindromCheck.charAt(string.length() - 1 - index)) {
    return false;
  }
}
return true;
}

Java Palindrome（布尔方法）与迭代解决方案（while循环）

5 个答案: