The document contains Java code examples illustrating new features introduced in Java 7, including string switch, numeric literals, multi-catch exceptions, try-with-resources, generics with type inference (diamond operator), variable arguments, and sorting algorithms utilizing Fork/Join framework as well as executor services. Each section is organized under distinct classes with a main method demonstrating the functionality and usage of the features. Overall, it serves as a tutorial or reference guide for developers looking to leverage Java 7 enhancements in their coding practices.

1. Java, Up to Date
Sources
Copyright © 2012 Akira Koyasu Some rights reserved.

2. StringInSwitch.java
1 p a c k a g e java7.coin;
2
3 p u b l i c c l a s s StringInSwitch {
4
5 p u b l i c s t a t i c v o i d main(String[] args) {
6 String flag = "aaa";
7 s w i t c h (flag) {
8 c a s e "aaa":
9 System. out .println("aaa");
10 break;
11 c a s e "bbb":
12 System. out .println("bbb");
13 break;
14 c a s e "ccc":
15 System. out .println("ccc");
16 break;
17 }
18 }
19 }
20 1
1

3. NumericLiteral.java
1 p a c k a g e java7.coin;
2
3 p u b l i c c l a s s NumericLiteral {
4
5 p u b l i c s t a t i c v o i d main(String[] args) {
6 i n t b = 0b1110; // binary (new!)
7
8 i n t o = 016; // octal
9 i n t d = 14; // decimal
10 i n t x = 0xE; // hexadecimal
11
12 System. out .println(b);
13 System. out .println(o);
14 System. out .println(d);
15 System. out .println(x);
16
17 i n t m = 1_000_000;
18 System. out .println(m);
19 }
20 }
21
2

4. Bond.java
1 p a c k a g e java7.coin;
2
3 p u b l i c c l a s s Bond {
4 p u b l i c s t a t i c v o i d main(String[] args) {
5 // Courtesy Josh Bloch
6 i n t bond =
7 0000_____________0000________0000000000000000__000000000000000000+
8 00000000_________00000000______000000000000000__0000000000000000000+
9 000____000_______000____000_____000_______0000__00______0+
10 000______000_____000______000_____________0000___00______0+
11 0000______0000___0000______0000___________0000_____0_____0+
12 0000______0000___0000______0000__________0000___________0+
13 0000______0000___0000______0000_________0000__0000000000+
14 0000______0000___0000______0000________0000+
15 000______000_____000______000________0000+
16 000____000_______000____000________00000+
17 00000000_________00000000_______0000000+
18 0000_____________0000________000000007;
19
20 System. out .println(bond);
21 }
22 }
23
3

5. MultiCatch.java
1 p a c k a g e java7.coin;
2
3 i m p o r t java7.coin.exception.Exception1;
8
9 p u b l i c c l a s s MultiCatch {
10
11 v o i d callFoo() {
12 try {
13 foo (); // throws Exception1, Exception2
14 } c a t c h (Exception1 | Exception2 e) {
15 e.printStackTrace();
16 }
17 }
18
19 v o i d callBar() t h r o w s SubException1, SubException2 {
20 try {
21 bar (); // throws SubException1, SubException2
22 } c a t c h (SuperException e) {
23 t h r o w e;
24 }
25 }
26
27 s t a t i c v o i d foo() t h r o w s Exception1, Exception2 {
28 }
29
30 s t a t i c v o i d bar() t h r o w s SubException1, SubException2 {
31 }
32 }
33
4

6. TryWithResources.java
1 p a c k a g e java7.coin;
2
3 i m p o r t java.io.File;
7
8 p u b l i c c l a s s TryWithResources {
9
10 p u b l i c s t a t i c v o i d main(String[] args) {
11 File file = n e w File("/path/to/file");
12 t r y (Writer writer = n e w FileWriter(file)) {
13 writer.write("hello!!");
14 } c a t c h (IOException e) {
15 e.printStackTrace();
16 }
17 }
18 }
19
5

7. Diamond.java
1 p a c k a g e java7.coin;
2
3 i m p o r t java.util.ArrayList;
7
8 p u b l i c c l a s s Diamond {
9
10 p u b l i c s t a t i c v o i d main(String[] args) {
11 @SuppressWarnings("unused")
12 Map<String, List<Integer>> map = n e w HashMap<>();
13 }
14
15 v o i d anonymous() {
16 // '<>' cannot be used with anonymous classes
17 List<String> list = n e w ArrayList<>() {}; // 匿名クラス
18 }
19
20 v o i d call() {
21 // The method doSomething(List<String>) in the type Diamond
22 // is not applicable for the arguments (ArrayList<Object>)
23 doSomething(n e w ArrayList<>()); // メソッド呼び出し
n
24
25 doOtherthing(n e w ArrayList<>());
n
26 }
27
28 v o i d doSomething(List<String> list) {
29 }
30
31 v o i d doOtherthing(List<Object> list) {
32 }
33 }
34
6

8. Varargs.java
1 p a c k a g e java7.coin;
2
3 i m p o r t java.util.Arrays;
5
6 p u b l i c c l a s s Varargs {
7
8 p u b l i c s t a t i c v o i d main(String[] args) {
9 List<String> b = Arrays. asList ("taro", "jiro", "saburo");
10 List<String> s = Arrays. asList ("haruko", "natsuko", "akiko");
11 // Type safety: A generic array of List<String>
12 // is created for a varargs parameter
13 pol (b, s);
14 notPol (b, s);
15 }
16
17 // Type safety: Potential heap pollution
18 // via varargs parameter strLists
19 s t a t i c v o i d pol(List<String>... strLists) {
20 // ...
21 }
22
23 @SafeVarargs
24 s t a t i c v o i d notPol(List<String>... strLists) {
25 // ...
26 }
27 }
28
7

9. MergeSortSimple.java
1 p a c k a g e java7.forkjoin;
2
3 i m p o r t java.util.Arrays;
6
7 p u b l i c c l a s s MergeSortSimple {
8
9 p u b l i c s t a t i c v o i d main(String[] args) {
10 Stopwatch stopwatch = n e w Stopwatch();
11
12 // ランダムなint配列
13 f i n a l i n t SIZE = 100_000_000;
14 i n t [] ints = n e w i n t [SIZE];
15 f o r (i n t i = 0; i < SIZE; i++) {
i
16 ints[i] = (i n t ) (Math. random () * 100_000);
i
17 }
18 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
19 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
20
21 stopwatch.start();
22 ints = sort (ints);
23 stopwatch.stop();
24
25 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
26 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
27 System. out .println("time: " + stopwatch);
28 }
29
30 s t a t i c i n t [] sort(i n t [] ints) {
i
31 i f (ints.length <= 2) {
32 r e t u r n sortDirect (ints);
33 } else {
34 i n t mid = (i n t ) (ints.length * 0.5);
i
35 i n t [] left = sort (Arrays. copyOf (ints, mid));
36 i n t [] right = sort (Arrays. copyOfRange (ints, mid, ints.length));
37 r e t u r n merge (left, right);
38 }
39 }
40
41 s t a t i c i n t [] sortDirect(i n t [] ints) {
i
42 i f (ints.length <= 1) {
43 r e t u r n ints;
44 } e l s e i f (ints.length == 2) {
45 i f (ints[0] > ints[1]) {
46 i n t g = ints[0];
47 ints[0] = ints[1];
48 ints[1] = g;
49 }
50 r e t u r n ints;
51 }
52 t h r o w n e w AssertionError();
53 }
54
55 s t a t i c i n t [] merge(i n t [] left, i n t [] right) {
i
56 i n t [] all = n e w i n t [left.length + right.length];
57
58 f o r (i n t i = 0, j = 0, k = 0; i < all.length; i++) {
i
59 i f (j < left.length && k < right.length) {
60 i n t l = left[j];
61 i n t r = right[k];
62 i f (l < r) {
63 all[i] = l;
64 j++;
65 } else {
66 all[i] = r;
67 k++;
68 }
69 } e l s e i f (j < left.length) {
70 all[i] = left[j];
8

10. MergeSortSimple.java
71 j++;
72 } e l s e i f (k < right.length) {
73 all[i] = right[k];
74 k++;
75 } else {
76 t h r o w n e w AssertionError();
77 }
78 }
79
80 r e t u r n all;
81 }
82 }
83
9

11. MergeSortByForkJoin.java
1 p a c k a g e java7.forkjoin;
2
3 i m p o r t java.util.Arrays;
8
9 p u b l i c c l a s s MergeSortByForkJoin {
10
11 p u b l i c s t a t i c v o i d main(String[] args) {
12 Stopwatch stopwatch = n e w Stopwatch();
13 ForkJoinPool pool = n e w ForkJoinPool();
14
15 // ランダムなint配列
16 f i n a l i n t SIZE = 100_000_000;
17 i n t [] ints = n e w i n t [SIZE];
18 f o r (i n t i = 0; i < SIZE; i++) {
i
19 ints[i] = (i n t ) (Math. random () * 100_000);
i
20 }
21 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
22 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
23
24 stopwatch.start();
25 ints = pool.invoke(n e w MergeSort(ints));
n
26 stopwatch.stop();
27
28 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
29 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
30 System. out .println("time: " + stopwatch);
31 }
32
33 s t a t i c c l a s s MergeSort e x t e n d s RecursiveTask<i n t []> {
i
34 p r i v a t e s t a t i c f i n a l l o n g serialVersionUID = 1L;
35
36 i n t [] ints;
37
38 MergeSort(i n t [] ints) {
i
39 t h i s .ints = ints;
40 }
41
42 @Override
43 p r o t e c t e d i n t [] compute() {
44 i f (ints.length <= 2) {
45 r e t u r n MergeSortSimple. sortDirect (ints);
46 } else {
47 i n t mid = (i n t ) (ints.length * 0.5);
i
48 MergeSort leftSort = n e w MergeSort(Arrays. copyOf (ints, mid));
49 MergeSort rightSort = n e w MergeSort(Arrays. copyOfRange (ints, mid, ints.length));
50 leftSort.fork();
51 i n t [] right = rightSort.compute();
52 i n t [] left = leftSort.join();
53 r e t u r n MergeSortSimple. merge (left, right);
54 }
55 }
56 }
57 }
58
10

12. MergeSortByExecutor.java
1 p a c k a g e java7.forkjoin;
2
3 i m p o r t java.util.Arrays;
14
15 p u b l i c c l a s s MergeSortByExecutor {
16
17 s t a t i c f i n a l i n t pros = Runtime. getRuntime ().availableProcessors();
18 s t a t i c f i n a l ExecutorService executor = Executors. newFixedThreadPool ( pros );
19
20 p u b l i c s t a t i c v o i d main(String[] args) {
21 Stopwatch stopwatch = n e w Stopwatch();
22
23 // ランダムなint配列
24 f i n a l i n t SIZE = 100_000_000;
25 i n t [] ints = n e w i n t [SIZE];
26 f o r (i n t i = 0; i < SIZE; i++) {
i
27 ints[i] = (i n t ) (Math. random () * 100_000);
i
28 }
29 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
30 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
31
32 stopwatch.start();
33 ints = divide (ints);
34 stopwatch.stop();
35
36 System. out .println("head: " + Arrays. toString (Arys. head (ints)));
37 System. out .println("tail: " + Arrays. toString (Arys. tail (ints)));
38 System. out .println("time: " + stopwatch);
39
40 executor .shutdown();
41 }
42
43 s t a t i c i n t [] divide(f i n a l i n t [] ints) {
f
44 List<Future<i n t []>> futureList = Lists. newArrayList ();
i
45 f i n a l i n t len = ints.length / pros ;
46 i n t i = 0;
47 f o r (; i < pros ; i++) {
48 f i n a l i n t fi = i;
49 futureList.add( executor .submit(n e w Callable<i n t []>() {
n i
50 @Override
51 p u b l i c i n t [] call() t h r o w s Exception {
52 r e t u r n MergeSortSimple. sort (Arrays. copyOfRange (ints, fi * len, (fi+1) * len));
53 }}));
54 }
55 f i n a l i n t fi = i;
56 futureList.add( executor .submit(n e w Callable<i n t []>() {
n i
57 @Override
58 p u b l i c i n t [] call() t h r o w s Exception {
59 r e t u r n MergeSortSimple. sort (Arrays. copyOfRange (ints, fi * len, ints.length));
60 }}));
61
62 try {
63 Iterator<Future<i n t []>> itr = futureList.iterator();
i
64 i n t [] left = itr.next().get();
65 w h i l e (itr.hasNext()) {
66 i n t [] right = itr.next().get();
67 left = MergeSortSimple. merge (left, right);
68 }
69 r e t u r n left;
70 } c a t c h (InterruptedException | ExecutionException e) {
71 e.printStackTrace();
72 }
73 t h r o w n e w AssertionError();
74 }
75 }
76
11

13. BasicUse.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.BufferedWriter;
11
12 p u b l i c c l a s s BasicUse {
13
14 p u b l i c s t a t i c v o i d main(String[] args) {
15 FileSystem fs = FileSystems. getDefault ();
16 Path path = fs.getPath("/path", "to", "file");
17
18 t r y (BufferedWriter bw = Files. newBufferedWriter (path,
19 StandardCharsets. UTF_8 , StandardOpenOption. CREATE )) {
20
21 bw.write("Oh, NIO.2 !!");
22
23 } c a t c h (IOException e) {
24 e.printStackTrace();
25 }
26 }
27 }
28
12

14. FilesSample.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.IOException;
9
10 p u b l i c c l a s s FilesSample {
11
12 p u b l i c s t a t i c v o i d main(String[] args) {
13 Path dir = Paths. get ("/path", "to");
14 Path path1 = Paths. get ("/path", "to", "file1");
15 Path path2 = Paths. get ("/path", "to", "file2");
16 Path link = Paths. get ("/path", "to", "link");
17
18 try {
19 Files. createFile (path1);
20 Files. createSymbolicLink (link, path1);
21 Files. copy (path1, path2, StandardCopyOption. COPY_ATTRIBUTES );
22 Files. move (path1, path2, StandardCopyOption. ATOMIC_MOVE );
23 @SuppressWarnings("unused")
24 b y t e [] bytes = Files. readAllBytes (path2);
25
26 t r y (DirectoryStream<Path> ds = Files. newDirectoryStream (dir)) {
27 f o r (Path path : ds) {
28 System. out .println(path);
29 }
30 }
31 } c a t c h (IOException e) {
32 e.printStackTrace();
33 }
34 }
35 }
36
13

15. AttributeViewSample.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.IOException;
11
12 p u b l i c c l a s s AttributeViewSample {
13
14 p u b l i c s t a t i c v o i d main(String[] args) {
15 Path path = Paths. get ("/path", "to", "file");
16 BasicFileAttributeView view
17 = Files. getFileAttributeView (path, BasicFileAttributeView.c l a s s );
c
18 PosixFileAttributeView view2
19 = Files. getFileAttributeView (path, PosixFileAttributeView.c l a s s );
c
20 try {
21 i f (view != n u l l ) {
22 BasicFileAttributes attributes = view.readAttributes();
23 System. out .println(attributes.creationTime());
24 System. out .println(attributes.lastModifiedTime());
25 System. out .println(attributes.lastAccessTime());
26 }
27 i f (view2 != n u l l ) {
28 PosixFileAttributes attributes2 = view2.readAttributes();
29 System. out .println(attributes2.owner());
30 System. out .println(attributes2.group());
31 System. out .println(attributes2.permissions());
32 }
33 } c a t c h (IOException e) {
34 e.printStackTrace();
35 }
36 }
37 }
38
14

16. FileVisitorSample.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.IOException;
10
11 p u b l i c c l a s s FileVisitorSample {
12
13 p u b l i c s t a t i c v o i d main(String[] args) {
14 try {
15 Path dir = Paths. get ("/path", "to", "dir");
16 Files. walkFileTree (dir, n e w SimpleFileVisitor<Path>() {
17 @Override
18 p u b l i c FileVisitResult preVisitDirectory(Path dir,
19 BasicFileAttributes attrs) t h r o w s IOException {
20 System. out .println("preVisitDir: " + dir);
21 r e t u r n FileVisitResult. CONTINUE ;
22 }
23
24 @Override
25 p u b l i c FileVisitResult postVisitDirectory(Path dir,
26 IOException exc) t h r o w s IOException {
27 System. out .println("postVisitDir: " + dir);
28 r e t u r n FileVisitResult. CONTINUE ;
29 }
30
31 @Override
32 p u b l i c FileVisitResult visitFile(Path file,
33 BasicFileAttributes attrs) t h r o w s IOException {
34 System. out .println("visitFile: " + file);
35 r e t u r n FileVisitResult. CONTINUE ;
36 }
37 });
38 } c a t c h (IOException e) {
39 e.printStackTrace();
40 }
41 }
42 }
43
15

17. WatchServiceSample.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.IOException;
11
12 p u b l i c c l a s s WatchServiceSample {
13
14 p u b l i c s t a t i c v o i d main(String[] args) {
15 FileSystem fs = FileSystems. getDefault ();
16 Path dir = fs.getPath("/path", "to", "dir");
17 try {
18 WatchService watcher = fs.newWatchService();
19 dir.register(watcher,
20 StandardWatchEventKinds. ENTRY_CREATE ,
21 StandardWatchEventKinds. ENTRY_MODIFY ,
22 StandardWatchEventKinds. ENTRY_DELETE );
23 b o o l e a n valid;
24 do {
25 WatchKey key = watcher.take(); // ブロック
26 f o r (WatchEvent<?> event : key.pollEvents()) {
27 i f (event.kind() == StandardWatchEventKinds. OVERFLOW ) {
28 System. out .println("overflow!!");
29 } else {
30 System. out .println(
31 event.kind() + " : " + event.context());
32 }
33 }
34 valid = key.reset();
35 } w h i l e (valid);
36 } c a t c h (IOException | InterruptedException e) {
37 e.printStackTrace();
38 }
39 }
40 }
41
16

18. AsynchronousSample.java
1 p a c k a g e java7.nio2;
2
3 i m p o r t java.io.FileInputStream;
15
16 p u b l i c c l a s s AsynchronousSample {
17
18 p u b l i c s t a t i c v o i d main(String[] args) {
19 t r y (InputStream in = n e w FileInputStream(
20 "/path/to/largeFile");) {
21 write (in).await();
22 } c a t c h (IOException | InterruptedException e) {
23 e.printStackTrace();
24 }
25 }
26
27 s t a t i c CountDownLatch write(InputStream in) {
28 ReadableByteChannel rbc = Channels. newChannel (in);
29 ByteBuffer buf = ByteBuffer. allocate (0x1000);
30
31 Path file = Paths. get ("/path", "to", "file");
32 CountDownLatch latch = n e w CountDownLatch(1);
33 try {
34 AsynchronousFileChannel afc =
35 AsynchronousFileChannel. open (file,
36 StandardOpenOption. CREATE ,
37 StandardOpenOption. WRITE );
38 i n t len;
39 i f ((len = rbc.read(buf)) > -1) {
40 buf.flip();
41 afc.write(buf, 0, buf, n e w WriteContinuing(rbc, afc, len, latch));
42 }
43 } c a t c h (IOException e) {
44 e.printStackTrace();
45 latch.countDown();
46 }
47 r e t u r n latch;
48 }
49
50 s t a t i c c l a s s WriteContinuing i m p l e m e n t s CompletionHandler<Integer, ByteBuffer> {
51 p r i v a t e f i n a l ReadableByteChannel rbc;
52 p r i v a t e f i n a l AsynchronousFileChannel afc;
53 p r i v a t e f i n a l i n t pos;
54 p r i v a t e f i n a l CountDownLatch latch;
55
56 p u b l i c WriteContinuing(
57 ReadableByteChannel rbc,
58 AsynchronousFileChannel afc,
59 i n t position,
60 CountDownLatch latch) {
61 t h i s .rbc = rbc;
62 t h i s .afc = afc;
63 t h i s .pos = position;
64 t h i s .latch = latch;
65 }
66
67 @Override
68 p u b l i c v o i d completed(Integer result, ByteBuffer buf) {
69 buf.clear();
70 try{
71 i n t len;
72 i f ((len = rbc.read(buf)) > -1) {
73 buf.flip();
74 afc.write(buf, pos, buf, n e w WriteContinuing(rbc, afc, pos + len, latch));
75 } else {
76 System. out .println("completed!");
77 afc.close();
78 latch.countDown();
79 }
17

19. AsynchronousSample.java
80 } c a t c h (IOException e) {
81 e.printStackTrace();
82 latch.countDown();
83 }
84 }
85
86 @Override
87 p u b l i c v o i d failed(Throwable exc, ByteBuffer buf) {
88 exc.printStackTrace();
89 }
90 }
91 }
92
18

20. Puzzle.java
1 p a c k a g e java7.puzzle;
2
3 i m p o r t java.util.Arrays;
5
6 p u b l i c c l a s s Puzzle {
7
8 p u b l i c s t a t i c v o i d main(String[] args) {
9 List<String>[] stringLists = n e w List<String>[10];
10 stringLists[0] = Arrays. asList ("first string!");
11 Object[] array = stringLists;
12 array[0] = Arrays. asList (0);
13 System. out .println(stringLists[0].get(0));
14 }
15 }
16
19

21. index.xhtml
1 <?xml version= "1.0" encoding= "UTF-8" ?>
2 <!DOCTYPE html>
3 <html xmlns:h= "http://java.sun.com/jsf/html" >
4 <head>
5 <title>Greeting</title>
6 </head>
7 <h:body>
8 #{myBean.greeting}
9 </h:body>
10 </html>
20

22. MyBean.java
1
2
3 i m p o r t javax.inject.Inject;
5
6 @Named
7 p u b l i c c l a s s MyBean {
8 @Inject
9 p r i v a t e MyService myService;
10
11 p u b l i c String getGreeting() {
12 r e t u r n myService.getGreeting();
13 }
14 }
15
21

23. MyService.java
1
2
3 i m p o r t javax.annotation.ManagedBean;
4
5 @ManagedBean
6 p u b l i c c l a s s MyService {
7 p u b l i c String getGreeting() {
8 r e t u r n "Hello JavaEE6!!";
9 }
10 }
11
22

24. beans.xml
1
23

25. faces-config.xml
1
24

26. Notes
This work is licensed under the Creative Commons Attribution-NonCommercial 3.0 Unported
License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/3.0/.
25