第Java關(guān)于JDK1.8新特性的Stream流ListStringemptyList=Arrays.asList("abc","","bc","efg","abcd","","");

//獲取空字符串的數(shù)量

longcount=emptyList.parallelStream().filter(string-string.isEmpty()).count();

System.out.println("*****集合中的空字符串個數(shù)="+count);

7、Collectors

Collectors類實現(xiàn)了很多歸約操作，例如將流轉(zhuǎn)換成集合和集合元素，Collectors可用于返回列表或字符串

ListStringorgCollectors=Arrays.asList("abc","","bc","efg","abcd","","jkl");

ListStringfiltered=orgCollectors.stream().filter(string-!string.isEmpty())

.collect(Collectors.toList());

System.out.println("篩選列表："+filtered);

StringmergedString=stringList.stream().filter(string-!string.isEmpty()).collect(Collectors.joining(","));

System.out.println("合并字符串："+mergedString);

統(tǒng)計：

//統(tǒng)計

ListIntegerorgNums=Arrays.asList(3,2,2,3,7,3,5);

IntSummaryStatisticsstatistics=numbers.stream().mapToInt((x)-x).summaryStatistics();

System.out.println("列表中最大的數(shù)："+statistics.getMax());

System.out.println("列表中最小的數(shù)："+statistics.getMin());

System.out.println("所有數(shù)之和："+statistics.getSum());

System.out.println("平均數(shù)："+statistics.getAverage());

8、轉(zhuǎn)化（將枚舉類轉(zhuǎn)成map）

將一個枚舉類轉(zhuǎn)成一個map，使用的示例可以參考下方：

MapInteger,StringdisableFlagMap=Arrays.stream(DisableFlagEnum.values()).collect(Collectors.toMap(p-p.getCode(),p-p.getDesc()));

完整的代碼是：

publicenumDisableFlagEnum{

NORMAL(0,"正常"),

DELETE(1,"已刪除");

privateIntegercode;

privateStringdesc;

DisableFlagEnum(Integercode,Stringdesc){

this.code=code;

this.desc=desc;

publicIntegergetCode(){

returncode;

publicStringgetDesc(){

returndesc;

publicstaticStringgetDesc(Integercode){

MapInteger,StringdisableFlagMap=Arrays.stream(DisableFlagEnum.values()).collect(Collectors.toMap(p-p.getCode(),p-p.getDesc()));

returndisableFlagMap.get(code);

demo的運行結(jié)果：

總結(jié)：

本文首先介紹了JDK1.8中的Stream流，Stream流是是一個來自數(shù)據(jù)源的元素隊列并支持聚合操作。它的特點就是中間過程不會存儲數(shù)據(jù)，不會改變數(shù)據(jù)源本身。接著介紹了str