If statement 未调用foreach中的Java-If语句
我试图检查某个字符串是否在字符串集合中。(本例中的字符串是来自activemq代理的主题)因此基本上我遍历主题列表,并将这些主题与搜索的主题进行比较(保存在变量“compare”中)。“topic.getTopicName()”明确地返回一个字符串,因此我不明白为什么变量计数没有设置为1,即使在一种情况下条件为true。因此IF子句中的语句永远不会执行。我是不是忽略了什么If statement 未调用foreach中的Java-If语句,if-statement,foreach,jms,activemq,broker,If Statement,Foreach,Jms,Activemq,Broker,我试图检查某个字符串是否在字符串集合中。(本例中的字符串是来自activemq代理的主题)因此基本上我遍历主题列表,并将这些主题与搜索的主题进行比较(保存在变量“compare”中)。“topic.getTopicName()”明确地返回一个字符串,因此我不明白为什么变量计数没有设置为1,即使在一种情况下条件为true。因此IF子句中的语句永远不会执行。我是不是忽略了什么 public ArrayList<String> getTopics() throws RemoteExcep
public ArrayList<String> getTopics() throws RemoteException {
try {
// get Topics as Strings from Broker
ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://localhost:61616");
ActiveMQConnection connection;
connection = (ActiveMQConnection) connectionFactory.createConnection();
connection.start();
DestinationSource ds = connection.getDestinationSource();
Set<ActiveMQTopic> topics = ds.getTopics();
String compare = "Physical";
int count = 0;
for(ActiveMQTopic topic : topics){
System.out.println(topic.getTopicName());
if(compare == topic.getTopicName()) {
System.out.println("Found " + topic.getTopicName());
count = count + 1;
}
}
if(count == 0){
System.out.println("No topic found");
}
else System.out.println("Topic found");
} catch (JMSException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public ArrayList getTopics()引发RemoteException{
试一试{
//从代理获取主题作为字符串
ActiveMQConnectionFactory connectionFactory=新的ActiveMQConnectionFactory(“tcp://localhost:61616");
ActiveMQConnection连接;
connection=(ActiveMQConnection)connectionFactory.createConnection();
connection.start();
DestinationSource ds=connection.getDestinationSource();
设置topics=ds.getTopics();
字符串compare=“Physical”;
整数计数=0;
for(ActiveMQTopic:topics){
System.out.println(topic.getTopicName());
if(compare==topic.getTopicName()){
System.out.println(“Found”+topic.getTopicName());
计数=计数+1;
}
}
如果(计数=0){
System.out.println(“未找到主题”);
}
else System.out.println(“找到主题”);
}捕获(JME){
//TODO自动生成的捕捉块
e、 printStackTrace();
}
返回null;
}
无法使用==运算符比较字符串。具体信息可在此处找到:
更改这行代码
if(compare == topic.getTopicName())
对此
if (compare.equals(topic.getTopicName())
无法使用==运算符比较字符串。具体信息可在此处找到: 更改这行代码
if(compare == topic.getTopicName())
对此
if (compare.equals(topic.getTopicName())
我无法完全调试您的代码,因为我不确定
ActiveMQConnectionFactory
中有什么内容,但我可以提供一些建议
尝试添加
if(compare == topic.getTopicName()) {
System.out.println("Found " + topic.getTopicName());
count = count + 1;
}
else {
System.out.println("Not Found " + topic.getTopicName());
}
下面是else语句,这样您就可以看到当它们应该相等时会发生什么。此外,我认为应该使用.equals()
而不是=
来比较字符串,因为字符串是对象
您可以在以下代码中看到使用==fail进行字符串比较:
public static void main(String[] args) {
String compare = "Physical";
String someString = new String("Physical");
String[] words = {"Test", "Cheese", "Physical", someString};
for (String s: words) {
if(s == compare) {
System.out.println(s + " == " + compare);
}
else {
System.out.println(s + " " + "!= " + compare);
}
}
System.out.println("---------------------------------------");
for (String s: words) {
if(s.equals(compare)) {
System.out.println(s + " == " + compare);
}
else {
System.out.println(s + " " + "!= " + compare);
}
}
}
印刷品
Test != Physical
Cheese != Physical
Physical == Physical
Physical != Physical
---------------------------------------
Test != Physical
Cheese != Physical
Physical == Physical
Physical == Physical
我无法完全调试您的代码,因为我不确定
ActiveMQConnectionFactory
中有什么内容,但我可以提供一些建议
尝试添加
if(compare == topic.getTopicName()) {
System.out.println("Found " + topic.getTopicName());
count = count + 1;
}
else {
System.out.println("Not Found " + topic.getTopicName());
}
下面是else语句,这样您就可以看到当它们应该相等时会发生什么。此外,我认为应该使用.equals()
而不是=
来比较字符串,因为字符串是对象
您可以在以下代码中看到使用==fail进行字符串比较:
public static void main(String[] args) {
String compare = "Physical";
String someString = new String("Physical");
String[] words = {"Test", "Cheese", "Physical", someString};
for (String s: words) {
if(s == compare) {
System.out.println(s + " == " + compare);
}
else {
System.out.println(s + " " + "!= " + compare);
}
}
System.out.println("---------------------------------------");
for (String s: words) {
if(s.equals(compare)) {
System.out.println(s + " == " + compare);
}
else {
System.out.println(s + " " + "!= " + compare);
}
}
}
印刷品
Test != Physical
Cheese != Physical
Physical == Physical
Physical != Physical
---------------------------------------
Test != Physical
Cheese != Physical
Physical == Physical
Physical == Physical
哦,我没有意识到这一点,我会试一试的。我没有意识到,我会试一试的