; map.put("123", "456"); map.put("789", "123"); System.out.println("如果存在就执行,并将结果作为value放入map"); map.computeIfPresent...("1234", (k, v) -> v + "1 "); // {123=456, 789=123} 说明未找到指定的key时无更改 System.out.println(map); map.computeIfPresent...v) -> v + "2 "); // {123=4562 , 789=123} 说明如果找到了对应的key,将value更改为后面的结果 System.out.println(map); map.computeIfPresent...null); // {789=123} 说明如果找到对应的key,并且后方传入Function内部apply返回值为null,则移除对应的key System.out.println(map); map.computeIfPresent...// {1234=null6 , 789=123} 说明如果key不存在,后方函数返回值为null时,不会更改map System.out.println(map); 现在基本理解了compute、computeIfPresent
暂且仅记录方法:compute, computeIfAbsent,computeIfPresent,putIfAbsent 基础 Method 形式 描述 实例 功能特性 compute default...map.computeIfAbsent(key, k -> new Value(f(k))); 新增 computeIfPresent default V computeIfPresent(K key,...map.computeIfPresent(1, (key, value) -> (key + 1) + value); 替换更新 putIfAbsent V putIfAbsent(K key,V value...= null) return map.putIfAbsent(key, newValue); } computeIfPresent if (map.get(key) !
extends V> mappingFunction) V computeIfPresent(K key, BiFunction<? super K, ? super V, ?...接口在1.8版本新增以下几个有趣的方法,今天参考源码来学习一下. getOrDefault replaceAll putIfAbsent remove replace computeIfAbsent computeIfPresent...extends V> remappingFunction) 当key存在时,计算新值,如果新值不为空,则将新值写入,如果新值为空,则移除掉此key.返回新值或者null. default V computeIfPresent...(1, (key, oldValue) -> key + oldValue + 2); // 3 不存在,不作操作 test.computeIfPresent(3, (key...而computeIfPresent传入key和旧的value,并且由他们两个计算得到新的值. V compute(K key, BiFunction<? super K, ? super V, ?
使用computeIfPresent方法 computeIfPresent方法可以在键存在时才计算新值,它接受一个键和一个BiFunction函数作为参数。...Map map = new HashMap(); map.put("apple", 1); map.computeIfPresent("apple", (key,...value) -> value + 1); // 更新键"apple"的值为2 map.computeIfPresent("banana", (key, value) -> value + 1); /
inappropriate"); map.computeIfAbsent("5", v -> "is exist"); System.out.println(map.get("5")); } computeIfPresent...hashmap.computeIfPresent(K key, BiFunction remappingFunction) 参数说明: key - 键 remappingFunction...例如: public static void computeIfPresent() { // 创建一个 HashMap HashMap prices =...System.out.println("HashMap: " + prices); // 重新计算鞋加上10%的增值税后的价值 int shoesPrice = prices.computeIfPresent
put(key, newValue); return newValue; } } return v; } Map.computeIfPresent...extends V> remappingFunction) Map.computeIfPresent 方法原型 V computeIfPresent(K key, BiFunction< ?...default V computeIfPresent(K key, BiFunction<? super K, ? super V, ?
words.forEach(word -> { map.putIfAbsent(word, 0); map.computeIfPresent(word, (w, prev) -> prev...prev + 1 : 1) ); compute()就像是computeIfPresent(),无论给定key是否存在都会调用它。如果键的值不存在,则prev参数为null。...operations.forEach(op -> { var key = op.getAccNo(); balances.putIfAbsent(key, BigDecimal.ZERO); balances.computeIfPresent
StatusUpdater.updateStatus public Mono updateStatus(InstanceId id) { return this.repository.computeIfPresent...(id, (key, instance) -> this.doUpdateStatus(instance)).then(); } repository.computeIfPresent 会调用EventsourcingInstanceRepository.computeIfPresent...EventsourcingInstanceRepository.computeIfPresent @Override public Mono computeIfPresent(InstanceId
小彩蛋 Map中的putIfAbsent、computeIfAbsent、computeIfPresent、compute put方法参考: public static void main(String...key -> null)); //3 key虽然不存在,但计算出为null,所以不作为,并且返回null System.out.println(map); //{1=3} } computeIfPresent...String[] args) { Map map = new HashMap(); System.out.println(map.computeIfPresent...("1", (k, v) -> Integer.valueOf(k) + v)); //null key不存在,不作为 且返回null System.out.println(map.computeIfPresent...把计算的结果覆盖掉,然后返回计算的结果 System.out.println(map); //{1=2} System.out.println(map.computeIfPresent
此示例展示如了何使用函数在 map 上计算代码: map.computeIfPresent(3, (num, val) -> val + num); map.get(3); //...val33 map.computeIfPresent(9, (num, val) -> null); map.containsKey(9); // false map.computeIfAbsent
当value存在时重新计算(computeIfPresent)public class MapTest { static class User { // 年龄 private...HashMap(); map.put(18, new User(18,"Yideng")); // 当存在key时,就重新计算value并赋值 map.computeIfPresent
= 0 && jvmUsed / jvmMax > threshold) { instanceCount.computeIfPresent(instanceName, (...= 0 && jvmUsed / jvmMax > threshold) { instanceCount.computeIfPresent(instanceName, (key, value) ->
map.computeIfAbsent(1, v -> new HashSet()).add("yi"); 使用computeIfAbsent()将条件判断和添加操作合二为一,使代码更加简洁. computeIfPresent...() 该方法签名为V computeIfPresent(K key, BiFunction<?...这个函数的功能跟如下代码是等效的: // Java7及以前跟computeIfPresent()等效的代码 if (map.get(key) !
sort() Map getOrDefault() forEach() replaceAll() putIfAbsent() remove() replace() computeIfAbsent() computeIfPresent...map.computeIfAbsent(1, v -> new HashSet()).add("yi"); 使用computeIfAbsent()将条件判断和添加操作合二为一,使代码更加简洁. map: computeIfPresent...()方法 V computeIfPresent(K key, BiFunction<?...不存在直接跳过,存在才插进去 这个函数的功能跟如下代码是等效的: // Java7及以前跟computeIfPresent()等效的代码 if (map.get(key) !
Invoker> setMethods = ReflectHelper.getFieldValue(reflector, "setMethods"); setMethods.computeIfPresent
exists"; }); fun.computeIfAbsent("list", (f -> new ArrayList())); fun.computeIfPresent
-> 9; default -> 0; }; 15 TreeMap新增方法 putIfAbsent computeIfAbsent computeIfPresent
AutoCloseable { void close() throws Exception; } Map userMap = xxxx; String name = userMap.computeIfPresent...(1, (k,v) -> "路人甲"); 1. compute的方法,不管key存不存在,操作完成后保存到map中; 2. computeIfPresent 的方法,对指定的在map中已经存在的key的
这个例子展示了如何利用函数来计算 map 上的代码: map.computeIfPresent(3, (num, val) -> val + num); map.get(3);...// val33 map.computeIfPresent(9, (num, val) -> null); map.containsKey(9); // false map.computeIfAbsent
, Integer> concurrentMap = new ConcurrentHashMap(); concurrentMap.put("Key1", 100); concurrentMap.computeIfPresent
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