Java集合之Map的示例代码详解

<p>public interface map<k,v> {<br/>    int size();//数目<br/>    boolean isempty();//判断是否为空<br/>    boolean containskey(<a href="http://www.php.cn/wiki/60.html" target="_blank">object</a> key);//判断是否含有某个key<br/>    boolean containsvalue(object value);//判断是否含有某个值<br/>    v get(object key);//通过key获得value<br/>    v put(k key, v value);//插入键值对<br/>    v remove(object key);//通过key<a href="http://www.php.cn/php/php-tp-remove.html" target="_blank">删除</a><br/>    void put<a href="http://www.php.cn/wiki/1483.html" target="_blank">all</a>(map<? <a href="http://www.php.cn/wiki/166.html" target="_blank">extends</a> k, ? extends v> m);//将一个map插入<br/>    void <a href="http://www.php.cn/wiki/917.html" target="_blank">clear</a>();//清空<br/>    <a href="http://www.php.cn/code/8209.html" target="_blank">set</a><k> keyset();//返回key集合<br/>    collection<v> values();//返回value<br/>    set<map.entry<k, v>> entryset();//实体集合，map的改变会影响到它<br/>    interface entry<k,v> {<br/>        k getkey();//获得key<br/>        v getvalue();//获得value<br/>        v setvalue(v value);//设置值<br/>        boolean equals(object o);//判断对象是否相等<br/>        int hashcode();//返回hashcode<br/>        //比较器，比较两个key<br/>        public <a href="http://www.php.cn/wiki/188.html" target="_blank">static</a> <k extends comparable<? <a href="http://www.php.cn/code/8202.html" target="_blank">super</a> k>, v> comparator<map.entry<k,v>> comparingbykey() {<br/>            <a href="http://www.php.cn/wiki/135.html" target="_blank">return</a> (comparator<map.entry<k, v>> & serializable)<br/>                    (c1, c2) -> c1.getkey().compareto(c2.getkey());<br/>        }<br/>        //比较两个值<br/>        public static <k, v extends comparable<? super v>> comparator<map.entry<k,v>> comparingbyvalue() {<br/>            return (comparator<map.entry<k, v>> & serializable)<br/>                    (c1, c2) -> c1.getvalue().compareto(c2.getvalue());<br/>        }<br/>        //比较两个key<br/>        public static <k, v> comparator<map.entry<k, v>> comparingbykey(comparator<? super k> cmp) {<br/>            objects.<a href="http://www.php.cn/wiki/136.html" target="_blank">require</a>non<a href="http://www.php.cn/wiki/62.html" target="_blank">null</a>(cmp);<br/>            return (comparator<map.entry<k, v>> & serializable)<br/>                    (c1, c2) -> cmp.compare(c1.getkey(), c2.getkey());<br/>        }<br/>        //比较两个值<br/>        public static <k, v> comparator<map.entry<k, v>> comparingbyvalue(comparator<? super v> cmp) {<br/>            objects.requirenonnull(cmp);<br/>            return (comparator<map.entry<k, v>> & serializable)<br/>                    (c1, c2) -> cmp.compare(c1.getvalue(), c2.getvalue());<br/>        }<br/>    }<br/>    //比较map是否相等<br/>    boolean equals(object o);<br/>    int hashcode();//hashcode<br/>    default v get<a href="http://www.php.cn/wiki/1360.html" target="_blank">ord</a>efault(object key, v defaultvalue) {<br/>        v v;<br/>        return (((v = get(key)) != null) || containskey(key))<br/>                ? v<br/>                : defaultvalue;<br/>    }<br/>    default void <a href="http://www.php.cn/wiki/127.html" target="_blank">foreach</a>(biconsumer<? super k, ? super v> <a href="http://www.php.cn/java/java-action.html" target="_blank">action</a>) {<br/>        objects.requirenonnull(action);<br/>        for (map.entry<k, v> entry : entryset()) {<br/>            k k;<br/>            v v;<br/>            try {<br/>                k = entry.getkey();<br/>                v = entry.getvalue();<br/>            } catch(illegalstate<a href="http://www.php.cn/wiki/265.html" target="_blank">exception</a> ise) {<br/>                // this usually means the entry is no longer in the map.<br/>                throw <a href="http://www.php.cn/wiki/165.html" target="_blank">new</a> con<a href="http://www.php.cn/wiki/1046.html" target="_blank">current</a>mod<a href="http://www.php.cn/wiki/109.html" target="_blank">if</a>icationexception(ise);<br/>            }<br/>            action.accept(k, v);<br/>        }<br/>    }<br/>    default void replaceall(bifunction<? super k, ? super v, ? extends v> function) {<br/>        objects.requirenonnull(function);<br/>        for (map.entry<k, v> entry : entryset()) {<br/>            k k;<br/>            v v;<br/>            try {<br/>                k = entry.getkey();<br/>                v = entry.getvalue();<br/>            } catch(illegalstateexception ise) {<br/>                // this usually means the entry is no longer in the map.<br/>                throw new concurrentmodificationexception(ise);<br/>            }<br/><br/>            // ise thrown from function is not a cme.<br/>            v = function.apply(k, v);<br/><br/>            try {<br/>                entry.setvalue(v);<br/>            } catch(illegalstateexception ise) {<br/>                // this usually means the entry is no longer in the map.<br/>                throw new concurrentmodificationexception(ise);<br/>            }<br/>        }<br/>    }<br/>    default v putifabsent(k key, v value) {<br/>        v v = get(key);<br/>        if (v == null) {<br/>            v = put(key, value);<br/>        }<br/><br/>        return v;<br/>    }<br/>    //删除某个key和value对应的对象<br/>    default boolean remove(object key, object value) {<br/>        object curvalue = get(key);<br/>        if (!objects.equals(curvalue, value) ||<br/>                (curvalue == null && !containskey(key))) {<br/>            return false;<br/>        }<br/>        remove(key);<br/>        return true;<br/>    }<br/>    //将某个key和oldvalue对应的值替换为newvalue<br/>    default boolean replace(k key, v oldvalue, v newvalue) {<br/>        object curvalue = get(key);<br/>        if (!objects.equals(curvalue, oldvalue) ||<br/>                (curvalue == null && !containskey(key))) {<br/>            return false;<br/>        }<br/>        put(key, newvalue);<br/>        return true;<br/>    }<br/>    //替换key的值<br/>    default v replace(k key, v value) {<br/>        v curvalue;<br/>        if (((curvalue = get(key)) != null) || containskey(key)) {<br/>            curvalue = put(key, value);<br/>        }<br/>        return curvalue;<br/>    }<br/>    default v computeifabsent(k key,<br/>                              function<? super k, ? extends v> mappingfunction) {<br/>        objects.requirenonnull(mappingfunction);<br/>        v v;<br/>        if ((v = get(key)) == null) {<br/>            v newvalue;<br/>            if ((newvalue = mappingfunction.apply(key)) != null) {<br/>                put(key, newvalue);<br/>                return newvalue;<br/>            }<br/>        }<br/><br/>        return v;<br/>    }<br/>    default v computeifpresent(k key,<br/>                               bifunction<? super k, ? super v, ? extends v> remappingfunction) {<br/>        objects.requirenonnull(remappingfunction);<br/>        v oldvalue;<br/>        if ((oldvalue = get(key)) != null) {<br/>            v newvalue = remappingfunction.apply(key, oldvalue);<br/>            if (newvalue != null) {<br/>                put(key, newvalue);<br/>                return newvalue;<br/>            } <a href="http://www.php.cn/wiki/111.html" target="_blank">else</a> {<br/>                remove(key);<br/>                return null;<br/>            }<br/>        } else {<br/>            return null;<br/>        }<br/>    }<br/>    default v compute(k key,<br/>                      bifunction<? super k, ? super v, ? extends v> remappingfunction) {<br/>        objects.requirenonnull(remappingfunction);<br/>        v oldvalue = get(key);<br/><br/>        v newvalue = remappingfunction.apply(key, oldvalue);<br/>        if (newvalue == null) {<br/>            // <a href="http://www.php.cn/wiki/1298.html" target="_blank">delete</a> mapping<br/>            if (oldvalue != null || containskey(key)) {<br/>                // something to remove<br/>                remove(key);<br/>                return null;<br/>            } else {<br/>                // nothing to do. leave things as they were.<br/>                return null;<br/>            }<br/>        } else {<br/>            // add or replace old mapping<br/>            put(key, newvalue);<br/>            return newvalue;<br/>        }<br/>    }<br/>    default v merge(k key, v value,<br/>                    bifunction<? super v, ? super v, ? extends v> remappingfunction) {<br/>        objects.requirenonnull(remappingfunction);<br/>        objects.requirenonnull(value);<br/>        v oldvalue = get(key);<br/>        v newvalue = (oldvalue == null) ? value :<br/>                remappingfunction.apply(oldvalue, value);<br/>        if(newvalue == null) {<br/>            remove(key);<br/>        } else {<br/>            put(key, newvalue);<br/>        }<br/>        return newvalue;<br/>    }<br/>}<br/></p>
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