「java在线解答」java代码详解
今天给各位分享java在线解答的知识，其中也会对java代码详解进行解释，如果能碰巧解决你现在面临的问题，别忘了关注本站，现在开始吧！
本文目录一览：
java在线解答
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
interface ElementJoiner {
public T String join(T[] ts, String delimiter);
public T String join(CollectionT ts, String delimiter);
}
public class ElementJoinerImpl implements ElementJoiner {
@Override
public T String join(T[] ts, String delimiter) {
StringBuilder sbd = new StringBuilder();
for (int i = 0; i ts.length; i++) {
sbd.append(String.valueOf(ts[i])).append(delimiter);
}
return sbd.substring(0, sbd.length() - delimiter.length());
}
@Override
public T String join(CollectionT ts, String delimiter) {
StringBuilder sbd = new StringBuilder();
IteratorT iter = ts.iterator();
while (iter.hasNext()) {
sbd.append(iter.next()).append(delimiter);
}
return sbd.substring(0, sbd.length() - delimiter.length());
}
public static void main(String[] args) {
Integer[] a = new Integer[10];
for (int i = 0; i a.length; i++) {
a[i] = i;
}
ElementJoinerImpl impl = new ElementJoinerImpl();
System.out.println(impl.join(a,"[HH]"));
System.out.println(impl.join(Arrays.asList(a),"|"));
}
}
java问题在线解答
您好，提问者：
我写的控制台的，你自己看一下吧。
import java.io.*;
public class CopyFile{
//异常我直接throws了，如有需要请自行修改
public static void main(String[] args)throws Exception{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("请输入源文件路径");
String str = null;
File file1 = new File(br.readLine());
if(!file1.exists()){
throw new RuntimeException("文件或者不存在！");
}
System.out.println("请输入目标文件路径");
File file2 = new File(br.readLine());
if(!file2.createNewFile()){
throw new RuntimeException("创建文件失败或者文件已存在！");
}
FileInputStream fis = new FileInputStream(file1);
FileOutputStream fos = new FileOutputStream(file2);
byte[] by = new byte[8192];
int len = 0;
while((len=fis.read(by))!=-1){
fos.write(by,0,len);
}
fos.close();
fis.close();
System.out.println("OK");
}
}
//测试结果：
请输入源文件路径
F:\a.txt
请输入目标文件路径
F:\aa.txt
OK
Java初学者问题，在线等，求解答。
什么也没改，帮你输出些信息，自己分析。
public class Sushu {
public static void main(String[] args) {
for (int i = 2; i = 100; i++) {
int temp = (int) Math.sqrt(i);
System.out.println("for:1 i = " + i + " ;temp = " + temp);
for (int j = 2; j = temp; j++) {
System.out.println("for:2 i = " + i + " ;j = " + j
+ " i%j = " + i % j);
if (i % j == 0) {
break;
}
System.out.println(j + " " + temp + " ------ " + (j temp)
+ " ------");
if (j temp) {
System.out.println(i);
}
}
}
}
}
结果：
for:1 i = 2 ;temp = 1
for:1 i = 3 ;temp = 1
for:1 i = 4 ;temp = 2
for:2 i = 4 ;j = 2 i%j = 0
for:1 i = 5 ;temp = 2
for:2 i = 5 ;j = 2 i%j = 1
2 2 ------ false ------
for:1 i = 6 ;temp = 2
for:2 i = 6 ;j = 2 i%j = 0
for:1 i = 7 ;temp = 2
for:2 i = 7 ;j = 2 i%j = 1
2 2 ------ false ------
for:1 i = 8 ;temp = 2
for:2 i = 8 ;j = 2 i%j = 0
for:1 i = 9 ;temp = 3
for:2 i = 9 ;j = 2 i%j = 1
2 3 ------ false ------
for:2 i = 9 ;j = 3 i%j = 0
for:1 i = 10 ;temp = 3
for:2 i = 10 ;j = 2 i%j = 0
for:1 i = 11 ;temp = 3
for:2 i = 11 ;j = 2 i%j = 1
2 3 ------ false ------
for:2 i = 11 ;j = 3 i%j = 2
3 3 ------ false ------
for:1 i = 12 ;temp = 3
for:2 i = 12 ;j = 2 i%j = 0
for:1 i = 13 ;temp = 3
for:2 i = 13 ;j = 2 i%j = 1
2 3 ------ false ------
for:2 i = 13 ;j = 3 i%j = 1
3 3 ------ false ------
for:1 i = 14 ;temp = 3
for:2 i = 14 ;j = 2 i%j = 0
for:1 i = 15 ;temp = 3
for:2 i = 15 ;j = 2 i%j = 1
2 3 ------ false ------
for:2 i = 15 ;j = 3 i%j = 0
for:1 i = 16 ;temp = 4
for:2 i = 16 ;j = 2 i%j = 0
for:1 i = 17 ;temp = 4
for:2 i = 17 ;j = 2 i%j = 1
2 4 ------ false ------
for:2 i = 17 ;j = 3 i%j = 2
3 4 ------ false ------
for:2 i = 17 ;j = 4 i%j = 1
4 4 ------ false ------
for:1 i = 18 ;temp = 4
for:2 i = 18 ;j = 2 i%j = 0
for:1 i = 19 ;temp = 4
for:2 i = 19 ;j = 2 i%j = 1
2 4 ------ false ------
for:2 i = 19 ;j = 3 i%j = 1
3 4 ------ false ------
for:2 i = 19 ;j = 4 i%j = 3
4 4 ------ false ------
for:1 i = 20 ;temp = 4
for:2 i = 20 ;j = 2 i%j = 0
for:1 i = 21 ;temp = 4
for:2 i = 21 ;j = 2 i%j = 1
2 4 ------ false ------
for:2 i = 21 ;j = 3 i%j = 0
for:1 i = 22 ;temp = 4
for:2 i = 22 ;j = 2 i%j = 0
for:1 i = 23 ;temp = 4
for:2 i = 23 ;j = 2 i%j = 1
2 4 ------ false ------
for:2 i = 23 ;j = 3 i%j = 2
3 4 ------ false ------
for:2 i = 23 ;j = 4 i%j = 3
4 4 ------ false ------
for:1 i = 24 ;temp = 4
for:2 i = 24 ;j = 2 i%j = 0
for:1 i = 25 ;temp = 5
for:2 i = 25 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 25 ;j = 3 i%j = 1
3 5 ------ false ------
for:2 i = 25 ;j = 4 i%j = 1
4 5 ------ false ------
for:2 i = 25 ;j = 5 i%j = 0
for:1 i = 26 ;temp = 5
for:2 i = 26 ;j = 2 i%j = 0
for:1 i = 27 ;temp = 5
for:2 i = 27 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 27 ;j = 3 i%j = 0
for:1 i = 28 ;temp = 5
for:2 i = 28 ;j = 2 i%j = 0
for:1 i = 29 ;temp = 5
for:2 i = 29 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 29 ;j = 3 i%j = 2
3 5 ------ false ------
for:2 i = 29 ;j = 4 i%j = 1
4 5 ------ false ------
for:2 i = 29 ;j = 5 i%j = 4
5 5 ------ false ------
for:1 i = 30 ;temp = 5
for:2 i = 30 ;j = 2 i%j = 0
for:1 i = 31 ;temp = 5
for:2 i = 31 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 31 ;j = 3 i%j = 1
3 5 ------ false ------
for:2 i = 31 ;j = 4 i%j = 3
4 5 ------ false ------
for:2 i = 31 ;j = 5 i%j = 1
5 5 ------ false ------
for:1 i = 32 ;temp = 5
for:2 i = 32 ;j = 2 i%j = 0
for:1 i = 33 ;temp = 5
for:2 i = 33 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 33 ;j = 3 i%j = 0
for:1 i = 34 ;temp = 5
for:2 i = 34 ;j = 2 i%j = 0
for:1 i = 35 ;temp = 5
for:2 i = 35 ;j = 2 i%j = 1
2 5 ------ false ------
for:2 i = 35 ;j = 3 i%j = 2
3 5 ------ false ------
for:2 i = 35 ;j = 4 i%j = 3
4 5 ------ false ------
for:2 i = 35 ;j = 5 i%j = 0
for:1 i = 36 ;temp = 6
for:2 i = 36 ;j = 2 i%j = 0
for:1 i = 37 ;temp = 6
for:2 i = 37 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 37 ;j = 3 i%j = 1
3 6 ------ false ------
for:2 i = 37 ;j = 4 i%j = 1
4 6 ------ false ------
for:2 i = 37 ;j = 5 i%j = 2
5 6 ------ false ------
for:2 i = 37 ;j = 6 i%j = 1
6 6 ------ false ------
for:1 i = 38 ;temp = 6
for:2 i = 38 ;j = 2 i%j = 0
for:1 i = 39 ;temp = 6
for:2 i = 39 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 39 ;j = 3 i%j = 0
for:1 i = 40 ;temp = 6
for:2 i = 40 ;j = 2 i%j = 0
for:1 i = 41 ;temp = 6
for:2 i = 41 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 41 ;j = 3 i%j = 2
3 6 ------ false ------
for:2 i = 41 ;j = 4 i%j = 1
4 6 ------ false ------
for:2 i = 41 ;j = 5 i%j = 1
5 6 ------ false ------
for:2 i = 41 ;j = 6 i%j = 5
6 6 ------ false ------
for:1 i = 42 ;temp = 6
for:2 i = 42 ;j = 2 i%j = 0
for:1 i = 43 ;temp = 6
for:2 i = 43 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 43 ;j = 3 i%j = 1
3 6 ------ false ------
for:2 i = 43 ;j = 4 i%j = 3
4 6 ------ false ------
for:2 i = 43 ;j = 5 i%j = 3
5 6 ------ false ------
for:2 i = 43 ;j = 6 i%j = 1
6 6 ------ false ------
for:1 i = 44 ;temp = 6
for:2 i = 44 ;j = 2 i%j = 0
for:1 i = 45 ;temp = 6
for:2 i = 45 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 45 ;j = 3 i%j = 0
for:1 i = 46 ;temp = 6
for:2 i = 46 ;j = 2 i%j = 0
for:1 i = 47 ;temp = 6
for:2 i = 47 ;j = 2 i%j = 1
2 6 ------ false ------
for:2 i = 47 ;j = 3 i%j = 2
3 6 ------ false ------
for:2 i = 47 ;j = 4 i%j = 3
4 6 ------ false ------
for:2 i = 47 ;j = 5 i%j = 2
5 6 ------ false ------
for:2 i = 47 ;j = 6 i%j = 5
6 6 ------ false ------
for:1 i = 48 ;temp = 6
for:2 i = 48 ;j = 2 i%j = 0
for:1 i = 49 ;temp = 7
for:2 i = 49 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 49 ;j = 3 i%j = 1
3 7 ------ false ------
for:2 i = 49 ;j = 4 i%j = 1
4 7 ------ false ------
for:2 i = 49 ;j = 5 i%j = 4
5 7 ------ false ------
for:2 i = 49 ;j = 6 i%j = 1
6 7 ------ false ------
for:2 i = 49 ;j = 7 i%j = 0
for:1 i = 50 ;temp = 7
for:2 i = 50 ;j = 2 i%j = 0
for:1 i = 51 ;temp = 7
for:2 i = 51 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 51 ;j = 3 i%j = 0
for:1 i = 52 ;temp = 7
for:2 i = 52 ;j = 2 i%j = 0
for:1 i = 53 ;temp = 7
for:2 i = 53 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 53 ;j = 3 i%j = 2
3 7 ------ false ------
for:2 i = 53 ;j = 4 i%j = 1
4 7 ------ false ------
for:2 i = 53 ;j = 5 i%j = 3
5 7 ------ false ------
for:2 i = 53 ;j = 6 i%j = 5
6 7 ------ false ------
for:2 i = 53 ;j = 7 i%j = 4
7 7 ------ false ------
for:1 i = 54 ;temp = 7
for:2 i = 54 ;j = 2 i%j = 0
for:1 i = 55 ;temp = 7
for:2 i = 55 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 55 ;j = 3 i%j = 1
3 7 ------ false ------
for:2 i = 55 ;j = 4 i%j = 3
4 7 ------ false ------
for:2 i = 55 ;j = 5 i%j = 0
for:1 i = 56 ;temp = 7
for:2 i = 56 ;j = 2 i%j = 0
for:1 i = 57 ;temp = 7
for:2 i = 57 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 57 ;j = 3 i%j = 0
for:1 i = 58 ;temp = 7
for:2 i = 58 ;j = 2 i%j = 0
for:1 i = 59 ;temp = 7
for:2 i = 59 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 59 ;j = 3 i%j = 2
3 7 ------ false ------
for:2 i = 59 ;j = 4 i%j = 3
4 7 ------ false ------
for:2 i = 59 ;j = 5 i%j = 4
5 7 ------ false ------
for:2 i = 59 ;j = 6 i%j = 5
6 7 ------ false ------
for:2 i = 59 ;j = 7 i%j = 3
7 7 ------ false ------
for:1 i = 60 ;temp = 7
for:2 i = 60 ;j = 2 i%j = 0
for:1 i = 61 ;temp = 7
for:2 i = 61 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 61 ;j = 3 i%j = 1
3 7 ------ false ------
for:2 i = 61 ;j = 4 i%j = 1
4 7 ------ false ------
for:2 i = 61 ;j = 5 i%j = 1
5 7 ------ false ------
for:2 i = 61 ;j = 6 i%j = 1
6 7 ------ false ------
for:2 i = 61 ;j = 7 i%j = 5
7 7 ------ false ------
for:1 i = 62 ;temp = 7
for:2 i = 62 ;j = 2 i%j = 0
for:1 i = 63 ;temp = 7
for:2 i = 63 ;j = 2 i%j = 1
2 7 ------ false ------
for:2 i = 63 ;j = 3 i%j = 0
for:1 i = 64 ;temp = 8
for:2 i = 64 ;j = 2 i%j = 0
for:1 i = 65 ;temp = 8
for:2 i = 65 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 65 ;j = 3 i%j = 2
3 8 ------ false ------
for:2 i = 65 ;j = 4 i%j = 1
4 8 ------ false ------
for:2 i = 65 ;j = 5 i%j = 0
for:1 i = 66 ;temp = 8
for:2 i = 66 ;j = 2 i%j = 0
for:1 i = 67 ;temp = 8
for:2 i = 67 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 67 ;j = 3 i%j = 1
3 8 ------ false ------
for:2 i = 67 ;j = 4 i%j = 3
4 8 ------ false ------
for:2 i = 67 ;j = 5 i%j = 2
5 8 ------ false ------
for:2 i = 67 ;j = 6 i%j = 1
6 8 ------ false ------
for:2 i = 67 ;j = 7 i%j = 4
7 8 ------ false ------
for:2 i = 67 ;j = 8 i%j = 3
8 8 ------ false ------
for:1 i = 68 ;temp = 8
for:2 i = 68 ;j = 2 i%j = 0
for:1 i = 69 ;temp = 8
for:2 i = 69 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 69 ;j = 3 i%j = 0
for:1 i = 70 ;temp = 8
for:2 i = 70 ;j = 2 i%j = 0
for:1 i = 71 ;temp = 8
for:2 i = 71 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 71 ;j = 3 i%j = 2
3 8 ------ false ------
for:2 i = 71 ;j = 4 i%j = 3
4 8 ------ false ------
for:2 i = 71 ;j = 5 i%j = 1
5 8 ------ false ------
for:2 i = 71 ;j = 6 i%j = 5
6 8 ------ false ------
for:2 i = 71 ;j = 7 i%j = 1
7 8 ------ false ------
for:2 i = 71 ;j = 8 i%j = 7
8 8 ------ false ------
for:1 i = 72 ;temp = 8
for:2 i = 72 ;j = 2 i%j = 0
for:1 i = 73 ;temp = 8
for:2 i = 73 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 73 ;j = 3 i%j = 1
3 8 ------ false ------
for:2 i = 73 ;j = 4 i%j = 1
4 8 ------ false ------
for:2 i = 73 ;j = 5 i%j = 3
5 8 ------ false ------
for:2 i = 73 ;j = 6 i%j = 1
6 8 ------ false ------
for:2 i = 73 ;j = 7 i%j = 3
7 8 ------ false ------
for:2 i = 73 ;j = 8 i%j = 1
8 8 ------ false ------
for:1 i = 74 ;temp = 8
for:2 i = 74 ;j = 2 i%j = 0
for:1 i = 75 ;temp = 8
for:2 i = 75 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 75 ;j = 3 i%j = 0
for:1 i = 76 ;temp = 8
for:2 i = 76 ;j = 2 i%j = 0
for:1 i = 77 ;temp = 8
for:2 i = 77 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 77 ;j = 3 i%j = 2
3 8 ------ false ------
for:2 i = 77 ;j = 4 i%j = 1
4 8 ------ false ------
for:2 i = 77 ;j = 5 i%j = 2
5 8 ------ false ------
for:2 i = 77 ;j = 6 i%j = 5
6 8 ------ false ------
for:2 i = 77 ;j = 7 i%j = 0
for:1 i = 78 ;temp = 8
for:2 i = 78 ;j = 2 i%j = 0
for:1 i = 79 ;temp = 8
for:2 i = 79 ;j = 2 i%j = 1
2 8 ------ false ------
for:2 i = 79 ;j = 3 i%j = 1
3 8 ------ false ------
for:2 i = 79 ;j = 4 i%j = 3
4 8 ------ false ------
for:2 i = 79 ;j = 5 i%j = 4
5 8 ------ false ------
for:2 i = 79 ;j = 6 i%j = 1
6 8 ------ false ------
for:2 i = 79 ;j = 7 i%j = 2
7 8 ------ false ------
for:2 i = 79 ;j = 8 i%j = 7
8 8 ------ false ------
for:1 i = 80 ;temp = 8
for:2 i = 80 ;j = 2 i%j = 0
for:1 i = 81 ;temp = 9
for:2 i = 81 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 81 ;j = 3 i%j = 0
for:1 i = 82 ;temp = 9
for:2 i = 82 ;j = 2 i%j = 0
for:1 i = 83 ;temp = 9
for:2 i = 83 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 83 ;j = 3 i%j = 2
3 9 ------ false ------
for:2 i = 83 ;j = 4 i%j = 3
4 9 ------ false ------
for:2 i = 83 ;j = 5 i%j = 3
5 9 ------ false ------
for:2 i = 83 ;j = 6 i%j = 5
6 9 ------ false ------
for:2 i = 83 ;j = 7 i%j = 6
7 9 ------ false ------
for:2 i = 83 ;j = 8 i%j = 3
8 9 ------ false ------
for:2 i = 83 ;j = 9 i%j = 2
9 9 ------ false ------
for:1 i = 84 ;temp = 9
for:2 i = 84 ;j = 2 i%j = 0
for:1 i = 85 ;temp = 9
for:2 i = 85 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 85 ;j = 3 i%j = 1
3 9 ------ false ------
for:2 i = 85 ;j = 4 i%j = 1
4 9 ------ false ------
for:2 i = 85 ;j = 5 i%j = 0
for:1 i = 86 ;temp = 9
for:2 i = 86 ;j = 2 i%j = 0
for:1 i = 87 ;temp = 9
for:2 i = 87 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 87 ;j = 3 i%j = 0
for:1 i = 88 ;temp = 9
for:2 i = 88 ;j = 2 i%j = 0
for:1 i = 89 ;temp = 9
for:2 i = 89 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 89 ;j = 3 i%j = 2
3 9 ------ false ------
for:2 i = 89 ;j = 4 i%j = 1
4 9 ------ false ------
for:2 i = 89 ;j = 5 i%j = 4
5 9 ------ false ------
for:2 i = 89 ;j = 6 i%j = 5
6 9 ------ false ------
for:2 i = 89 ;j = 7 i%j = 5
7 9 ------ false ------
for:2 i = 89 ;j = 8 i%j = 1
8 9 ------ false ------
for:2 i = 89 ;j = 9 i%j = 8
9 9 ------ false ------
for:1 i = 90 ;temp = 9
for:2 i = 90 ;j = 2 i%j = 0
for:1 i = 91 ;temp = 9
for:2 i = 91 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 91 ;j = 3 i%j = 1
3 9 ------ false ------
for:2 i = 91 ;j = 4 i%j = 3
4 9 ------ false ------
for:2 i = 91 ;j = 5 i%j = 1
5 9 ------ false ------
for:2 i = 91 ;j = 6 i%j = 1
6 9 ------ false ------
for:2 i = 91 ;j = 7 i%j = 0
for:1 i = 92 ;temp = 9
for:2 i = 92 ;j = 2 i%j = 0
for:1 i = 93 ;temp = 9
for:2 i = 93 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 93 ;j = 3 i%j = 0
for:1 i = 94 ;temp = 9
for:2 i = 94 ;j = 2 i%j = 0
for:1 i = 95 ;temp = 9
for:2 i = 95 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 95 ;j = 3 i%j = 2
3 9 ------ false ------
for:2 i = 95 ;j = 4 i%j = 3
4 9 ------ false ------
for:2 i = 95 ;j = 5 i%j = 0
for:1 i = 96 ;temp = 9
for:2 i = 96 ;j = 2 i%j = 0
for:1 i = 97 ;temp = 9
for:2 i = 97 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 97 ;j = 3 i%j = 1
3 9 ------ false ------
for:2 i = 97 ;j = 4 i%j = 1
4 9 ------ false ------
for:2 i = 97 ;j = 5 i%j = 2
5 9 ------ false ------
for:2 i = 97 ;j = 6 i%j = 1
6 9 ------ false ------
for:2 i = 97 ;j = 7 i%j = 6
7 9 ------ false ------
for:2 i = 97 ;j = 8 i%j = 1
8 9 ------ false ------
for:2 i = 97 ;j = 9 i%j = 7
9 9 ------ false ------
for:1 i = 98 ;temp = 9
for:2 i = 98 ;j = 2 i%j = 0
for:1 i = 99 ;temp = 9
for:2 i = 99 ;j = 2 i%j = 1
2 9 ------ false ------
for:2 i = 99 ;j = 3 i%j = 0
for:1 i = 100 ;temp = 10
for:2 i = 100 ;j = 2 i%j = 0
在线java问题解答
在JAVA程序设计中，事件的处理是非常重要的，尤其是在需要自定义事件和设计JavaBean时.对事件的处理过程有一个完整的认识对于编程是很有帮助的。
下面用一个演示性的例子来说明事件及其处理过程
一.事件的组成
如果想要自定义一个事件，则必须提供一个事件的监听接口以及一个事件类。在JAVA中监听接口继承java.util.EventListener,事件类继承java.util.EventObject.很多基本的事件在编程环境中都已经提供可以很方便使用，但是在自定义事件中必须要要了解这些。
下面是一个事件类的代码,事件类可以向用户处理程序提供被监听类的信息
import java.util.*;
public class PropertyEvent extends EventObject {
public PropertyEvent(){}
}
下面是监听接口的代码
import java.util.*;
public interface PropertyListener extends EventListener {
public void propertyChanged(PropertyEvent propertyEvent);
}
二.事件的处理机制
下面是一段简要的被监听类代码，通过代码分析事件处理过程
import java.util.*;
public class Exam {
private int property;
//listeners用来存放已注册的监听对象
private Set listeners= new HashSet();
.....
public void addListener(PropertyListener propertyListener){
//listeners必须保证只能被一个线程访问
synchronized(listeners){
listeners.add(propertyListener);
}
}
public void firePropertyChange(){
Iterator iterator;
synchronized(listeners){
//将listeners中的类名放到iterator
iterator = new HashSet(listeners).iterator();
}
//创建事件类
PropertyEvent propertyEvent = new PropertyEvent();
while(iterator.hasNext()){
PropertyListener propertyListener = (propertyListener) iterator.next();
//调用用户的事件处理程序
propertyListener.propertyChanged(propertyEvent);
}
}
}
当属性值发生变化时，首先进行内部处理调用firePropertyChange方法，产生一个事件对象然后用事件对象为参数来调用用户的事件处理程序。
三.事件处理的使用
1.基本用法
public Exam exam;
exam.addListener(this);
public void propertyChange(PropertyEvent event){...}
注：exam是被监听对象，this为监听对象，是已经实现了接口方法的当前类，addListener
将当前类注册到listeners.
2.一个被监听对象可以有多个监听对象
exam.addListener(listener1);
exam.addListener(listener2);
这样当exam的property发生变化时，actionListener1和actionListener2的处理程序都会
被调用。当然listener1和listener2必须都是已实现接口方法的类。
3.被监听的对象也可以是实现了方法的接口
exam.addListener(
new PropertyListener(){
//用户定义事件处理过程
public void propertyChange(PropertyEvent event){
...
}
);
这种方法在实际编程中非常方便。
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