[Java知识库]QMap类、 QHash类

QMap与QHash差别：

①QHash比QMap查找速度更快。
②QHash以任意顺序存储，QMap以Key顺序存储数据。
③QHash的Key必须提供operator==()及一个全局的qHash(Key)函数，而QMap的Key必须提供operator<()函数。
存储一键多值数据时可使用QMultiMap<Key,T>容器或QMultiHash<Key,T>容器。
Java风格迭代器

STL风格迭代器

#include <QCoreApplication>
#include <QMap>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QMap<QString,QString> infoMap;

    //添加数据
    infoMap.insert("王祖蓝","163cm");
    infoMap.insert("Anglebaby","168cm");
    infoMap["易烊千玺"] = "173cm(成长中)";
    infoMap["姚明"] = "226cm";

    //通过key找value
    qDebug() << "姚明:" << infoMap["姚明"];
    qDebug() << "易烊千玺:" << infoMap.value("易烊千玺");

    //通过value找key
    qDebug() << "168cm的是谁呢？"
             << infoMap.key("168cm")
             << endl;

    //Java风格只读迭代器
    QMapIterator<QString,QString> it_r(infoMap);
    for(it_r.toFront();it_r.hasNext();)
    {
        it_r.next();
        qDebug() << it_r.key() << ":" << it_r.value();
    }

    //Java风格读写迭代器
    QMutableMapIterator<QString,QString> it_rw(infoMap);
    if(it_rw.findNext("163cm"))
        it_rw.setValue("163.1cm");

    qDebug() << endl << "修改数据后遍历：";
    for(it_rw.toFront();it_rw.hasNext();)
    {
        it_rw.next();
        qDebug() << it_rw.key() <<":" << it_rw.value();
    }

    QMap<QString,QString> wMap;
    wMap.insert("spring","15℃");
    wMap.insert("summer","35℃");
    wMap.insert("autumn","23℃");
    wMap.insert("winter","-5℃");

    //STL风格只读迭代器
    QMap<QString,QString>::const_iterator i_r;
    i_r = wMap.constBegin();

    qDebug() << endl << "初始化季节遍历:";
    for( ; i_r != wMap.constEnd(); ++i_r)
        qDebug() << i_r.key() << ":" << i_r.value();

    //STL风格读写迭代器
    QMap<QString,QString>::iterator i_rw;
    i_rw = wMap.find("spring");
    if(i_rw != wMap.end())
        i_rw.value() = "16℃";

    qDebug() << endl << "修改春天的数据后遍历：";
    i_rw = wMap.begin();
    for( ; i_rw != wMap.end(); ++i_rw)
        qDebug() << i_rw.key() << ":" << i_rw.value();

    QMultiMap<QString,QString> wMap1;
    wMap1.insert("spring","15℃");
    wMap1.insert("summer","35℃");
    wMap1.insert("summer","39℃");
    wMap1.insert("summer","40℃");
    wMap1.insert("autumn","23℃");
    wMap1.insert("winter","-5℃");
    wMap1.insert("winter","-15℃");
    wMap1.insert("winter","-55℃");

    qDebug() << endl << "初始化wMap1：" << wMap1;

    wMap1.remove("winter","-55℃");
    qDebug() << endl << "删除winter:-55℃后" << wMap1;

    qDebug() << endl << "winter:"
             <<wMap1.values("winter");

    //Java风格只读迭代
    QMapIterator<QString,QString> i_r1(wMap1);

    qDebug() << endl << "初始化季节遍历：";
    for(i_r1.toFront(); i_r1.hasNext();)
        qDebug() << i_r1.key()
                 << ":"
                 << i_r1.next().value();


    //QHash类
    QHash<int,QString> moneyHash;
    moneyHash.insert(1,"一块钱");
    moneyHash.insert(10,"十块钱");
    moneyHash.insert(20,"二十块钱");
    moneyHash[50] = "五十块钱";
    moneyHash[100] = "一百块钱";
    moneyHash.insertMulti(100,"毛爷爷");

    //Java风格只读迭代器
    QHashIterator<int,QString> it_mr(moneyHash);

    qDebug() << endl << "只读正遍历人民币：";
    for(it_mr.toFront(); it_mr.hasNext();)
        qDebug() << it_mr.key()
                 << ":"
                 << it_mr.next().value();

    //Java风格读写迭代器
    QMutableHashIterator<int,QString> it_mrw(moneyHash);

    //修改数据
    if( it_mrw.findNext("十块钱") )
        it_mrw.setValue("10元");

    qDebug() << endl << "更新10元后遍历：";
    for(it_mrw.toFront(); it_mrw.hasNext();)
        qDebug() << it_mrw.key()
                 << ":"
                 << it_mrw.next().value();

    return a.exec();
}