java streams

1the Stream API is used to process collections
2of objects. A stream is a sequence of objects
3that supports various methods which can be
4pipelined to produce the desired result.
5  It is very similar to build().perform() 
6  method in Actions class. It is chaining
7  some operations in an order.
8
9The features of Java stream are:
10- A stream is not a data structure instead
11it takes input from the Collections, 
12Arrays or I/O channels.
13- Streams don’t change the original data
14structure, they only provide the result
15as per the pipelined methods.
16- Each intermediate operation is lazily
17executed and returns a stream as a result,
18hence various intermediate operations
19can be pipelined. Terminal operations mark
20the end of the stream and return the result.
21
22Different Operations On Streams:
23
24map ==> The map method is used to return a
25stream consisting of the results of applying
26the given function to the elements of this stream.
27List number = Arrays.asList(2,3,4,5);
28List square = number.stream().map(x->x*x).collect(Collectors.toList());
29
30filter ==> The filter method is used to
31select elements as per the Predicate passed as argument.
32List names = Arrays.asList("Reflection","Collection","Stream");
33List result = names.stream().filter(s->s.startsWith("S")).collect(Collectors.toList());
34
35sorted ==> The sorted method is used to sort the stream.
36List names = Arrays.asList("Reflection","Collection","Stream");
37List result = names.stream().sorted().collect(Collectors.toList());
38
39ArrayList<String> list3 = new ArrayList(Arrays.asList("monkey", "donkey","onion"));
40List<String> list4 = list3.stream().filter(each->!"onion".equals(each)).collect(Collectors.toList());
41System.out.println(list4);
42
43static String reverse(String word){
44    return Arrays.stream(word.split("")).reduce("", (x,y) -> y+x );
45}

1import java.io.*;
2public class CopyFile {
3
4   public static void main(String args[]) throws IOException {  
5      FileInputStream in = null;
6      FileOutputStream out = null;
7
8      try {
9         in = new FileInputStream("input.txt");
10         out = new FileOutputStream("output.txt");
11         
12         int c;
13         while ((c = in.read()) != -1) {
14            out.write(c);
15         }
16      }finally {
17         if (in != null) {
18            in.close();
19         }
20         if (out != null) {
21            out.close();
22         }
23      }
24   }
25}

1public class StreamBuilders 
2{
3     public static void main(String[] args)
4     {
5         Stream<Integer> stream = Stream.of( new Integer[]{1,2,3,4,5,6,7,8,9} );
6         stream.forEach(p -> System.out.println(p));
7     }
8}
9

1Arrays.asList("a1", "a2", "a3")
2    .stream()
3    .findFirst()
4    .ifPresent(System.out::println);  // a1
5

1public class Employee {
2
3	private int employeeID;
4	private String employeeName;
5	private String employeeGender;
6	private String employeeCountry;
7	private String employeeState;
8	private String employeeCity;
9	
10	public Employee() {
11		// TODO Auto-generated constructor stub
12	}
13
14	public Employee(int employeeID, String employeeName, String employeeGender, String employeeCountry,
15			String employeeState, String employeeCity) {
16		super();
17		this.employeeID = employeeID;
18		this.employeeName = employeeName;
19		this.employeeGender = employeeGender;
20		this.employeeCountry = employeeCountry;
21		this.employeeState = employeeState;
22		this.employeeCity = employeeCity;
23	}
24
25	public int getEmployeeID() {
26		return employeeID;
27	}
28
29	public void setEmployeeID(int employeeID) {
30		this.employeeID = employeeID;
31	}
32
33	public String getEmployeeName() {
34		return employeeName;
35	}
36
37	public void setEmployeeName(String employeeName) {
38		this.employeeName = employeeName;
39	}
40
41	public String getEmployeeGender() {
42		return employeeGender;
43	}
44
45	public void setEmployeeGender(String employeeGender) {
46		this.employeeGender = employeeGender;
47	}
48
49	public String getEmployeeCountry() {
50		return employeeCountry;
51	}
52
53	public void setEmployeeCountry(String employeeCountry) {
54		this.employeeCountry = employeeCountry;
55	}
56
57	public String getEmployeeState() {
58		return employeeState;
59	}
60
61	public void setEmployeeState(String employeeState) {
62		this.employeeState = employeeState;
63	}
64
65	public String getEmployeeCity() {
66		return employeeCity;
67	}
68
69	public void setEmployeeCity(String employeeCity) {
70		this.employeeCity = employeeCity;
71	}
72
73	@Override
74	public String toString() {
75		// TODO Auto-generated method stub
76		return "[Employee ID : " + employeeID + ", Employee Name : " + employeeName + ", Employee Gender : "
77				+ employeeGender + ", Employee Country : " + employeeCountry + ", Employee State : " + employeeState
78				+ ", Employee City : " + employeeCity + "]";
79	}
80	
81	public static void main(String[] args) {
82		ArrayList<Employee> employees=new ArrayList<Employee>();
83		
84		employees.add(new Employee(101, "John", "M", "United States", "California", "Los Angeles"));
85		employees.add(new Employee(91, "Jacob", "M", "United States", "California", "Los Angeles"));
86		employees.add(new Employee(111, "Lisa", "F", "United States", "California", "Los Angeles"));
87		employees.add(new Employee(97, "Mary", "F", "United States", "California", "Sacramento"));
88		employees.add(new Employee(76, "Christine", "F", "United States", "California", "Sacramento"));
89		employees.add(new Employee(114, "David", "M", "United States", "California", "San Jose"));
90		employees.add(new Employee(103, "Kevin", "M", "United States", "California", "Oakland"));
91		employees.add(new Employee(109, "Joe", "M", "United States", "California", "Oakland"));
92		employees.add(new Employee(119, "Mathew", "M", "United States", "California", "San Jose"));
93		employees.add(new Employee(99, "Angelina", "F", "United States", "California", "San Diego"));
94		employees.add(new Employee(98, "Tom", "M", "United States", "California", "San Diego"));
95		employees.add(new Employee(116, "Curl", "M", "United States", "California", "Los Angeles"));
96		employees.add(new Employee(66, "Christopher", "M", "United States", "California", "Oakland"));
97		employees.add(new Employee(56, "Chelse", "F", "United States", "California", "Oakland"));
98		employees.add(new Employee(88, "Murali", "M", "United States", "California", "San Jose"));
99		employees.add(new Employee(87, "Daisy", "F", "United States", "California", "Sacramento"));
100		employees.add(new Employee(85, "Niza", "F", "United States", "Virginia", "Richmond"));
101		employees.add(new Employee(86, "Chris", "M", "United States", "Virginia", "Fairfax"));
102		employees.add(new Employee(90, "Andrew", "M", "United States", "Virginia", "Reston"));
103		
104	}
105
106}
107
108Operations:
109
1101. Get list of all the employees from "California"; Return a List
1112. Count the number of Females; Return a Count
1123. Add 10 to the ID of each Employee; Return the updated List
1134. Sort in the Descending order by employee name (z-a); Return the List
1145. Get the details of the second highest employee ID; Return the employee
115
116Solution:
117
118System.out.println(employees.stream().filter(employee->employee.getEmployeeState().equals("California")).collect(Collectors.toList()));
119System.out.println(employees.stream().map(emp->emp.getEmployeeID()+10).collect(Collectors.toList()));
120System.out.println(employees.stream().filter(employee->employee.getEmployeeGender().equalsIgnoreCase("f")).count());
121System.out.println(employees.stream().sorted((e1,e2)->e2.getEmployeeName().compareTo(e1.getEmployeeName())).collect(Collectors.toList()));
122Collections.sort(employees, (s1,s2)-> s2.getEmployeeID() - s1.getEmployeeID());
123System.out.println(employees.get(1));

1
2package com.mkyong.java8;
3
4import java.util.stream.IntStream;
5
6public class ParallelExample3a {
7
8    public static void main(String[] args) {
9
10        System.out.println("Normal...");
11
12        IntStream range = IntStream.rangeClosed(1, 10);
13        System.out.println(range.isParallel());         // false
14        range.forEach(System.out::println);
15
16        System.out.println("Parallel...");
17
18        IntStream range2 = IntStream.rangeClosed(1, 10);
19        IntStream range2Parallel = range2.parallel();
20        System.out.println(range2Parallel.isParallel()); // true
21        range2Parallel.forEach(System.out::println);
22
23    }
24
25}
26