我写了一个应用程序,它工作了3年,但是!今天,当他们尝试运行此应用程序时,出现了意外的异常:
INFO | jvm 1 | 2013/04/17 10:02:40 | Exception in thread "Thread-1" java.lang.NoSuchMethodError: java.sql.Connection.isValid(I)Z
INFO | jvm 1 | 2013/04/17 10:02:40 | at lib.MySQLConnectionPatch.SearchInCache(MySQLConnectionPatch.java:103)
INFO | jvm 1 | 2013/04/17 10:02:40 | at lib.MySQLConnectionPatch.getConnection(MySQLConnectionPatch.java:79)
INFO | jvm 1 | 2013/04/17 10:02:40 | at lib.SQLManager.establishSqlConnection(SQLManager.java:62)
INFO | jvm 1 | 2013/04/17 10:02:40 | at lib.SQLManager.establishSqlConnection(SQLManager.java:30)
INFO | jvm 1 | 2013/04/17 10:02:40 | at lib.tasks.classes.sql.executeQuery.execute(executeQuery.java:49)
INFO | jvm 1 | 2013/04/17 10:02:40 | at Components.TTask.run(TTask.java:86)
INFO | jvm 1 | …考虑这个java类:
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
public class NumberSet {
private Collection<? extends Number> numbers;
public NumberSet(Collection<? extends Number> numbers) {
this.numbers = numbers;
}
public NumberSet(NumberSet other) {
//copy other.numbers to this.numbers
numbers = new LinkedList<>();
for (Iterator<? extends Number> it = other.numbers.iterator(); it.hasNext();) {
numbers.add(it.next()); // Here's Syntax Error near `it.next()`
}
}
}
for循环内部存在此语法错误:
actual argument Number cannot be converted to CAP#1 by method invocation conversion
where E is a type-variable:
E extends Object declared …