J2SE 8的流库 --- 基本类型流的使用

展现流的方法

public static <T> void show(String title, Stream<T> stream){
	System.out.println("title:"+title);

	List<T> collect = stream.limit(10).collect(Collectors.toList());
	collect.forEach(n->System.out.println(n));
	System.out.println();
}

创建公共的list

ArrayList<String> arrayList = new ArrayList<>();
arrayList.add("aa");
arrayList.add("bb");
arrayList.add("cc");

Random random = new Random();

1. IntStream

//(1)创建IntStream
IntStream intStream = IntStream.of(1,1,2,3,4);
show("intStream", intStream.boxed());		//boxed()	基本类型流->对象流

intStream = IntStream.range(0, 5);		//[int startInclusive, int endExclusive),不包括5
show("intStream", intStream.boxed());

intStream = IntStream.rangeClosed(0, 5);	//[int startInclusive, int endExclusive],包括5
show("intStream", intStream.boxed());

intStream = IntStream.generate(()->new Random().nextInt());
show("intStream", intStream.boxed());

intStream = IntStream.iterate(0, n->n+8);
show("intStream", intStream.boxed());

IntStream mapToIntStream = arrayList.stream().mapToInt(String::length);		//mapToInt	将对象流->基本类型流
show("mapToIntStream", mapToIntStream.boxed());

//codePoints->IntStream
IntStream codePointsIntStream = "世界上很好听的纯音乐（经典不朽）".codePoints();
show("codePointsIntStream", codePointsIntStream.boxed());	

//charsIntStream->IntStream
IntStream charsIntStream = "世界上很好听的纯音乐（经典不朽）".chars();
show("charsIntStream", charsIntStream.boxed());

//产生随机数流
IntStream randomIntStream = random.ints();
show("randomIntStream", randomIntStream.boxed());

randomIntStream = random.ints(3);			//指定stream size 3
show("randomIntStream", randomIntStream.boxed());

randomIntStream = random.ints(10, 15);		//指定起点10, 边界15
show("randomIntStream", randomIntStream.boxed());

randomIntStream = random.ints(8, 10, 15);	//指定stream size 8, 指定起点10, 边界15
show("randomIntStream", randomIntStream.boxed());

//(2)得到平均值， 和， 最大值， 最小值
//使用Supplier<T> 包装流,防止得到流已使用/关闭错误
Supplier<IntStream> intStreamSupplier = () -> IntStream.of(1,1,2,3,4);
System.out.println("intStream.average()		"+intStreamSupplier.get().average().getAsDouble());
System.out.println("intStream.sum()			"+intStreamSupplier.get().sum());
System.out.println("intStream.max()			"+intStreamSupplier.get().max().getAsInt());
System.out.println("intStream.min()			"+intStreamSupplier.get().min().getAsInt());

IntSummaryStatistics intSummaryStatistics = intStreamSupplier.get().summaryStatistics();
System.out.println("intStream.average()		"+intSummaryStatistics.getAverage());
System.out.println("intStream.sum()			"+intSummaryStatistics.getSum());
System.out.println("intStream.max()			"+intSummaryStatistics.getMax());
System.out.println("intStream.min()			"+intSummaryStatistics.getMin());
System.out.println();

//(3) IntStream -> 数组
int[] arrayIntStream = intStreamSupplier.get().toArray();
System.out.println("arrayIntStream	"+Arrays.toString(arrayIntStream));
System.out.println();

//(4) mapToObjStream
Stream<String[]> mapToObjStream = IntStream.range(0, 15).mapToObj(x->new String[]{"asdas","vfvfvc","43fg","fgfg"});
mapToObjStream.forEach((x)->System.out.println(Arrays.toString(x)));
System.out.println();

2. LongStream

//(1)创建LongStream
LongStream longStream = LongStream.of(1,1,2,3,4);
show("longStream", longStream.boxed());		//boxed()	基本类型流->对象流

longStream = LongStream.range(0, 5);		//[int startInclusive, int endExclusive),不包括5
show("longStream", longStream.boxed());

longStream = LongStream.rangeClosed(0, 5);	//[int startInclusive, int endExclusive],包括5
show("longStream", longStream.boxed());

longStream = LongStream.generate(()->new Random().nextLong());
show("longStream", longStream.boxed());

longStream = LongStream.iterate(0, n->n+8);
show("longStream", longStream.boxed());

LongStream mapToLongStream = arrayList.stream().mapToLong(x->(long)x.length());		//mapToLong	将对象流->基本类型流
show("mapToLongStream", mapToLongStream.boxed());	

//产生随机数流
LongStream randomLongStream = random.longs();
show("randomLongStream", randomLongStream.boxed());

randomLongStream = random.longs(3);				//指定stream size 3
show("randomLongStream", randomLongStream.boxed());

randomLongStream = random.longs(10, 15);		//指定起点10, 边界15
show("randomLongStream", randomLongStream.boxed());

randomLongStream = random.longs(8, 10, 15);		//指定stream size 8, 指定起点10, 边界15
show("randomLongStream", randomLongStream.boxed());

//(2)得到平均值， 和， 最大值， 最小值
//使用Supplier<T> 包装流
Supplier<LongStream> longStreamSupplier = () -> LongStream.of(1,1,2,3,4);
System.out.println("longStream.average()		"+longStreamSupplier.get().average().getAsDouble());
System.out.println("longStream.sum()			"+longStreamSupplier.get().sum());
System.out.println("longStream.max()			"+longStreamSupplier.get().max().getAsLong());
System.out.println("longStream.min()			"+longStreamSupplier.get().min().getAsLong());

LongSummaryStatistics longSummaryStatistics = longStreamSupplier.get().summaryStatistics();
System.out.println("longStream.average()		"+longSummaryStatistics.getAverage());
System.out.println("longStream.sum()			"+longSummaryStatistics.getSum());
System.out.println("longStream.max()			"+longSummaryStatistics.getMax());
System.out.println("longStream.min()			"+longSummaryStatistics.getMin());
System.out.println();

//(3) LongStream -> 数组
long[] arrayLongStream = longStreamSupplier.get().toArray();
System.out.println("arrayLongStream	"+Arrays.toString(arrayLongStream));
System.out.println();

3. DoubleStream

//(1)创建DoubleStream
DoubleStream doubleStream = DoubleStream.of(1.1,1.2,1.3,2.1,2.2);
show("doubleStream", doubleStream.boxed());

doubleStream = DoubleStream.generate(Math::random);
show("doubleStream", doubleStream.boxed());

doubleStream = DoubleStream.iterate(1.1, n->n+1.1);
show("doubleStream", doubleStream.boxed());

DoubleStream mapToDoubleStream = arrayList.stream().mapToDouble(x->(double)x.length());		//mapToDouble	将对象流->基本类型流
show("mapToDoubleStream", mapToDoubleStream.boxed());	

//产生随机数流
DoubleStream randomDoubleStream = random.doubles();
show("randomDoubleStream", randomDoubleStream.boxed());

randomDoubleStream = random.doubles(3);					//指定stream size 3
show("randomDoubleStream", randomDoubleStream.boxed());

randomDoubleStream = random.doubles(10.0, 15.0);		//指定起点10, 边界15
show("randomDoubleStream", randomDoubleStream.boxed());

randomDoubleStream = random.doubles(8, 10.0, 15.0);		//指定stream size 8, 指定起点10, 边界15
show("randomDoubleStream", randomDoubleStream.boxed());

//(2)得到平均值， 和， 最大值， 最小值
//使用Supplier<T> 包装流
Supplier<DoubleStream> doubleStreamSupplier = () -> DoubleStream.of(1.1,1.2,1.3,2.1,2.2);
System.out.println("doubleStream.average()		"+doubleStreamSupplier.get().average().getAsDouble());
System.out.println("doubleStream.sum()			"+doubleStreamSupplier.get().sum());
System.out.println("doubleStream.max()			"+doubleStreamSupplier.get().max().getAsDouble());
System.out.println("doubleStream.min()			"+doubleStreamSupplier.get().min().getAsDouble());

DoubleSummaryStatistics doubleSummaryStatistics = doubleStreamSupplier.get().summaryStatistics();
System.out.println("doubleStream.average()		"+doubleSummaryStatistics.getAverage());
System.out.println("doubleStream.sum()			"+doubleSummaryStatistics.getSum());
System.out.println("doubleStream.max()			"+doubleSummaryStatistics.getMax());
System.out.println("doubleStream.min()			"+doubleSummaryStatistics.getMin());
System.out.println();

//(3) LongStream -> 数组
double[] arrayDoubleStream = doubleStreamSupplier.get().toArray();
System.out.println("arrayDoubleStream	"+Arrays.toString(arrayDoubleStream));
System.out.println();

4. 对应的，创建short,char,byte,boolean,float流

Stream<Boolean> booleanStream = Arrays.stream(new Boolean[]{true,false,false,true});
show("booleanStream", booleanStream);