Streams are very basic in java 8 features . Below is my example where I'm going to cover different API methods . public class StreamBuilders { public static void main(String[] args){ List list = new ArrayList(); for(int i = 1; i< 10; i++){ list.add(i); } Stream stream = list.stream(); // stream count long count=list.stream().count(); //limit System.out.println("fileter value :"+ list.stream().filter(i->i>5).count()); System.out.println("count is "+count); List evenNumbersList = stream.filter(i -> i%2 == 0).collect(Collectors.toList()); System.out.print(evenNumbersList); // filter operations List nameList = Arrays.asList("Ram", "Amit", "Ashok", "Manish", "Rajat"); nameList.stream().filter(n->n.startsWith("A")).collect(Collectors.toList()).forEach(System.out::println); nameList.stream().filter(n -> !n.startsWith("A")).collect(Collectors.toList()).forEach(System.out::println); //map list.stream().map(n->n*2).filter(n->n>10).forEach(System.out::println); //complex operations List persons = Arrays.asList( new Person("Max", 18,"10000","computers"), new Person("Peter", 23,"15000","maths"), new Person("Pamela", 23,"17000","computers"), new Person("David", 12,"10000","physics")); // grouping the objects with age Listp1= persons.stream().filter(n->n.name.startsWith("P")).collect(Collectors.toList()); System.out.println(p1); Map> personWithGroupBy=persons.stream().collect(Collectors.groupingBy(p->p.age)); personWithGroupBy.forEach((age,p)->System.out.format("age %s: %s\n", age, p)); //grouping the persons with department Map> personsWithGroupByDept=persons.stream().collect(Collectors.groupingBy(Person::getDept)); personsWithGroupByDept.forEach((dept,p)->System.out.println(" dept : "+dept+" "+p)); // grouping the persons with salary Map> personWithSalary= persons.stream().collect(Collectors.groupingBy(p->p.salary)); personWithSalary.forEach((salary,p)->System.out.println("salary :"+salary+" "+p)); Map> personWithDept=persons.stream().collect(Collectors.groupingBy(p->p.dept)); personWithDept.forEach((dept,p)->System.out.println("dept : "+dept+ " "+p)); //sorting persons based on person name persons.sort(Comparator.comparing(p->p.name)); System.out.println("sorted list "+persons); persons.sort(Comparator.comparing(p->p.dept)); System.out.println("sorted with dept "+persons); } } class Person { public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getSalary() { return salary; } public void setSalary(String salary) { this.salary = salary; } public String getDept() { return dept; } public void setDept(String dept) { this.dept = dept; } String name; int age; String salary; String dept; Person(String name, int age,String salary,String dept) { this.name = name; this.age = age; this.salary=salary; this.dept=dept; } @Override public String toString() { return name +" "+salary+" " +dept+" "+age; } } /* out put : c:\rajesh\MicroServices\Java8Practice>java StreamBuilders fileter value :4 count is 9 [2, 4, 6, 8]Amit Ashok Ram Manish Rajat 12 14 16 18 [Peter 15000 maths 23, Pamela 17000 computers 23] age 18: [Max 10000 computers 18] age 23: [Peter 15000 maths 23, Pamela 17000 computers 23] age 12: [David 10000 physics 12] dept : maths [Peter 15000 maths 23] dept : physics [David 10000 physics 12] dept : computers [Max 10000 computers 18, Pamela 17000 computers 23] salary :17000 [Pamela 17000 computers 23] salary :15000 [Peter 15000 maths 23] salary :10000 [Max 10000 computers 18, David 10000 physics 12] dept : maths [Peter 15000 maths 23] dept : physics [David 10000 physics 12] dept : computers [Max 10000 computers 18, Pamela 17000 computers 23] sorted list [David 10000 physics 12, Max 10000 computers 18, Pamela 17000 computers 23, Peter 15000 maths 23] sorted with dept [Max 10000 computers 18, Pamela 17000 computers 23, Peter 15000 maths 23, David 10000 physics 12] */

rajeshjaava

Java 8 Streams

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