-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathStreamBase.java
More file actions
206 lines (169 loc) · 6.48 KB
/
StreamBase.java
File metadata and controls
206 lines (169 loc) · 6.48 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
package example.StreamExample;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* Stream 範例
*
* Reference
* - https://mrbird.cc/java8stream1.html
* - https://blog.tonycube.com/2015/10/java-java8-3-stream.html
* - https://www.runoob.com/java/java8-streams.html
*/
public class StreamBase {
public static void main(String[] args) {
List<String> list = Arrays.asList("Java", "JavaScript", "python", "PHP", "C#", "Golang", "Swift");
List<Integer> num = Arrays.asList(1, 2, 1, 3, 3, 2, 4);
findJChangeBig(list);
List<String> res = dealWithStream(list);
res.forEach(s -> {
System.out.println(s);
});
List<String> res2 = changeUpperCase(res);
res2.forEach(s2 -> {
System.out.println(s2);
});
// StreamTask streamTask = new StreamTask();
// streamTask.filterShapAndShow(list);
// streamTask.distinctEven(num);
System.out.println(changeLowerCase(list));
System.out.println("--------------");
useCollect();
useCollectJoining();
useMap();
useFilter();
}
// ! 傳統作法使用for-loop一個一個處理
public static void findJChangeBig(List<String> list) {
List<String> filterList = new ArrayList<>();
for (String str : list) {
if (str.startsWith("J")) {
filterList.add(str.toUpperCase());
}
}
for (String str : filterList) {
System.out.println(str);
}
}
// ! 使用stream來解決問題
public static List<String> dealWithStream(List<String> list) {
List<String> res = new ArrayList<>();
res = list.stream()
.filter(s -> s.startsWith("J"))
.collect(Collectors.toList());
// .map(String::toUpperCase)
// .forEach(System.out::println);
return res;
}
public static List<String> changeUpperCase(List<String> list) {
// ? 可以思考使用 Stream<String> 方式處理
List<String> res = new ArrayList<>();
list.stream()
.map(String::toUpperCase)
.forEach(res::add);
return res;
}
public static List<String> changeLowerCase(List<String> list) {
// ? 可以思考使用 Stream<String> 方式處理
List<String> res = new ArrayList<>();
list.stream()
.map(String::toLowerCase)
.forEach(res::add);
return res;
}
public static void useCollect() {
// use collect.
List<String> names = Stream.of("Tom", "Tony", "John")
.collect(Collectors.toList());
System.out.println("names: " + names.toString() + "; " + names.getClass().getTypeName());
List<String> names2 = Arrays.asList("Tom", "Tony", "John");
System.out.println("names2 " + names2 + "; " + names2.getClass());
}
public static void useCollectJoining() {
// https://blog.tonycube.com/2015/10/java-java8-3-stream.html
List<String> names = Arrays.asList("Tom", "Tony", "John");
String result = names.stream()
.map(n -> n + n)
.collect(Collectors.joining(",", "[", "]"));
System.out.println(result); // [TomTom,TonyTony,JohnJohn]
}
public static void useMap() {
// TODO: use map.
// 使用時機: 資料的轉換。當你有一個方法(method)它的用途會將某個輸入資料轉換成另一個資料輸出時，map 可以讓你使用這個方法。
// 輸入輸出：T -> R
List<Integer> ages = Stream.of(11, 2, 40, 37, 100, 27)
.collect(Collectors.toList());
// ! 注意 integer convert to string.
String result = (String) ages.stream()
.map(a -> String.valueOf(a+10))
.collect(Collectors.joining(",", "[", "]"));
System.out.println(result);
}
public static void useFilter() {
// ! great handle data style.
List<String> names = Arrays.asList("Tom", "Tony", "John", "George", "May", "Peter", "GG");
// * 範例1.
List<String> result = names.stream()
.filter(name -> name.startsWith("G"))
.collect(Collectors.toList());
System.out.println(result);
// * 範例2.
List<String> result2 = names.stream()
.filter(n -> n.contains("Tom"))
.collect(Collectors.toList());
System.out.println(result2);
// * 範例3.
List<String> result3 = names.stream()
.filter(n -> !"George".equals(n))
.collect(Collectors.toList());
System.out.println(result3);
// ? [Think] how to filter through a JSON document using Java 8 Stream API?
}
public void useContains() {
// TODO: use contains() to check statement in stream().
// * Reference: https://stackoverflow.com/questions/35200250/java-contains-vs-anymatch-behaviour/35200414
}
public void useAnyMatch() {
// TODO: use anyMatch() to check statement in stream().
// ! it seems the same as contains.
// * Reference: https://stackoverflow.com/questions/35200250/java-contains-vs-anymatch-behaviour/35200414
// you need to consider this sitution that no such elemeent exception when looking for a match in a List.
// * Reference: https://stackoverflow.com/questions/36346409/nosuchelementexception-when-looking-for-a-match-in-a-list
}
public void useFlatMap() {
// TODO: use flatMap.
}
public void useCount() {
// TODO: use count.
}
public void useMaxMin() {
// TODO: use Max and Min.
}
public void useSorted() {
// TODO: use sorted.
}
public void useSequential() {
// TODO: use sequential.
// https://blog.tonycube.com/2015/10/java-java8-3-stream.html
// ! 可以比較 sequential 和 parallel 差異。
}
public void useParallel() {
// TODO: use parallel.
// https://blog.tonycube.com/2015/10/java-java8-3-stream.html
}
}
class StreamTask {
public void filterShapAndShow(List<String> list) {
list.stream()
.filter(s -> s.contains("#"))
.forEach(System.out::println);
}
public void distinctEven(List<Integer> num) {
num.stream()
.filter(i -> i % 2 == 0)
.distinct()
.forEach(i -> System.out.println(i));
}
}