小编J.O*_*sen的帖子

当尝试比较作为参数传递的两个对象时:首先作为对象,第二个作为对象数组(相同类型).得到错误Incompatible conditional operand types Room and allRooms[].我试图循环迭代,while直到thisRoomType不等于某个对象rooms.怎么解决？

public abstract class Room { ...}
public class LightRoom extends Room  {...}
public class DarkRoom extends Room {...}

呼叫者:

release(thisRoomType, rooms)

带参数

private Room thisRoomType = this; // is defined in DarkRoom and LightRoom 
private Room[] rooms; // is defined in DarkRoom and LightRoom 

在方法中:

public synchronized void release( Room thisRoom,  Room[] allRooms) {

        try {
            int j = 0;
            while(thisRoom instanceof allRooms[j]){     
                jj++;
            } …

尝试序列化并将Lot对象发送到套接字.得到错误:

java.io.NotSerializableException: com.server.ClientServiceThread

为什么？

public class ClientServiceThread extends Thread  {... // form here called sendObj ...}

public class FlattenLot {
public void sendObj(){
        try {
            out = new ObjectOutputStream(oStream);
            out.writeObject(lot); // error
            out.flush();
            out.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

批次类:

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import java.util.Date;
import java.util.Calendar;

public class Lot implements Serializable{
private static final long serialVersionUID = 1L;
    public ArrayList<ClientServiceThread> clientBidsLog = new ArrayList<ClientServiceThread>();
    public ArrayList<Integer> bidLog = new ArrayList<Integer>();

    private …

我需要domain在 PostgreSQL 中创建一个价格。价格必须是NUMERIC(9,2)9 为精度，2 为小数位数。尝试创建域时获取：

ERROR: operator does not exist: numeric ~* unknown Hint: No operator matches the given name and argument type(s). You might need to add explicit type casts.

询问：

CREATE DOMAIN d_price AS NUMERIC(9, 2) NOT NULL 
CONSTRAINT Product_price_can_contain_only_double_precision_value
CHECK(VALUE ~*'^(([[:digit:]])+\.([[:digit:]]){2})$');

我无法摆脱错误:

  HTTP Status 500 - Request processing failed; nested exception is 
org.springframework.beans.BeanInstantiationException: 
Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]: 
No default constructor found; 
nested exception is java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()

我实际上有DSLR类的构造函数.我的代码出了什么问题？

代码在这里> Spring MVC WebApp:http://goo.gl/ddhLg5

可能导致错误的DSLR类:

package main.java.com.springapp.mvc.model;

import org.springframework.beans.factory.annotation.Autowired;

    public class DSLR {


    public DSLR() {
    }


    private int dslrId;
    private String model;
    private int price;
    private String description;

    public int getDslrId() {
        return dslrId;
    }

    public void setDslrId(int dslrId) {
        this.dslrId = dslrId;
    }

    public String getModel() { …

我有错误:"构造函数GeoPoint(double,double)未定义".为什么会这样？怎么做对了？据我所知,所有必要的库链接,语法似乎是正确的.

package com.fewpeople.geoplanner;

import android.app.Activity;
import android.os.Bundle;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;

public class GeoplannerActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        final MapView mMapView = (MapView) findViewById(R.id.mapview);

     MapController mMapController = mMapView.getController();

     double x, y;
     x= 60.113337;
     y= 55.151317;

     mMapController.animateTo(new GeoPoint(x, y));

     mMapController.setZoom(15);

    }

    protected boolean isRouteDisplayed() {
        return false;
    }
}

我需要从表单输入中获取值.保存到var.获取用户输入的长度.而不是我收到的字符数undefined.两个警报都返回相同undefined.为什么？

var aisbn = $('#aisbn').val();
alert(aisbn.lenght);
alert(aisbn.toString().lenght);

我需要在提交表单时发出GET ajax请求.不应重新加载页面.试图附加jQuery .submit()处理程序但由于某种原因这不起作用.为什么？

...
 $('#login-form').submit(function(){
            e.preventDefault();
            alert('Hi');
                   ....
         });
...

<form id="login-form" class="navbar-form" action="" method="get" >
                            <input id="email" class="span2" type="text" placeholder="Email">
                            <input id="password" class="span2" type="password" placeholder="Password">
                            <button type="submit" id="login-btn" class="btn btn-primary">Sign in</button>

                        </form >

基于链表建立队列实现.由于两个错误,无法运行应用程序:

public class Queue<Integer> implements Iterable<Integer> {
    ...
    public Iterator<Integer> iterator()  {
            return new ListIterator(first);
        }
    private class ListIterator<Integer> implements Iterator<Integer> {// error #1
            private Node<Integer> current;

            public ListIterator(Node<Integer> first) {
                current = first;
            }

            public boolean hasNext(){ return current != null;                   }
            public void remove()    { throw new UnsupportedOperationException();}

            public int next() { // error #2
                if (!hasNext()) throw new NoSuchElementException();
                int item = current.item;
                current = current.next;
                return item;
            }
        }    
     }

错误#1:错误:Queue.ListIterator不是抽象的,并且不会覆盖Iterator中的抽象方法next(),其中Integer是一个类型变量:Integer extends类Queue.ListIterator中声明的Object

错误#2:错误:next()在Queue.ListIterator中无法实现next()在Iterator中返回类型int与Integer不兼容,其中E,Integer是类型变量:E extends …

我有二进制搜索树,必须执行三种类型的树遍历:这个结果是否正确？

Pre-order (root,left,right): 30,15,59,43,40,92

In-order (left,root,right): 15,30,59,40,43,92

Post-order (left,right,root): 15,59,40,43,92,30

更新:

有序: 15,30,40,43,59,92(投影？)

下订单: 15,40,43,92,59,30.

这样对吗？

The exception is thrown when trying to suspend HikariCP pool while simulating network connection fail for a couple of seconds. Why can the pool cannot be suspended? Are there other easy ways to simulate lost network connection (to MySQL server on localhost)?

Configuration:

final String configFile = "src/main/resources/db.properties";
HikariConfig config = new HikariConfig(configFile);
config.setRegisterMbeans(true);
config.setPoolName("hikari-pool-1");
ds = new HikariDataSource(config);

Properties:

jdbcUrl=jdbc:mysql://localhost:3306/db?user=user&password=password
dataSource.prepStmtCacheSize=250
dataSource.prepStmtCacheSqlLimit=2048
dataSource.useServerPrepStmts=true
dataSource.useLocalSessionState=true
dataSource.useLocalTransactionState=true
dataSource.rewriteBatchedStatements=true
dataSource.cacheResultSetMetadata=true
dataSource.cacheServerConfiguration=true
dataSource.elideSetAutoCommits=true
dataSource.maintainTimeStats=false

JUnit:

MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();
ObjectName poolName = …