int x
int y
public Point() {
}
public Point(int x, int y) {
this.x = x
this.y = y
}
public Point(int x) {
this.x = x
this.y = x
}
public double distance() {//求当前点到原点的距离
return Math.sqrt((x * x + y * y))
}
public double distance(int x1, int y1) {//求当前点到（x1,y1）的距离
return Math.sqrt((x-x1)*(x-x1) + (y-y1) * (y-y1))
}
public double distance(Point other){
int x2 = other.x
int y2 = other.y
return Math.sqrt((x-x2)*(x-x2) + (y-y2) * (y-y2))
}
}
第二题
一个doDemo方法搞定
这个是列出D盘下所有文件及文件目录，然后再列出所有的.txt后缀的文件。
static List<String> allList = new ArrayList<String>()static List<String> txtList = new ArrayList<String>()
public static void doDemo() {
File file = new File("D:" + File.separator)
if (null == file)
return
allList.clear()
txtList.clear()
listAllFile(file)
for (String p : allList) {
System.out.println("file: " + p)
}
for (String txt : txtList) {
System.out.println("txt file: " + txt)
}
}
public static void listAllFile(File dir) {
if (null == dir || !dir.exists()) {
return
}
if (dir.isDirectory()) {
File[] files = dir.listFiles()
if (null != files) {
for (int i = 0 i < files.length i++) {
if (files[i].isDirectory()) {
listAllFile(files[i])
} else {
String fileName = files[i].getName()
if (fileName.endsWith(".txt")) {
txtList.add(files[i].getPath())
}
allList.add(files[i].getPath())
}
}
}
} else {
allList.add(dir.getPath())
}
}
public class BookTest{ public static void main(String[] args){Book book = new Book("Cook book",150) book.detail() }} class Book{ private String title private int pageNumpublic Book(String title,int pageNum){ this.title = title this.judgePage(pageNum) }public String getTitle(){ return this.title } public void setTitle(String title){ this.title=title }public int getPageNum(){ return this.pageNum }public void setPageNum(int pageNum){this.pageNum=this.judgePage(pageNum)}private int judgePage(int pageNum){if(pageNum<200){System.out.println("页数["+pageNum+"]不能小于200") pageNum = 200} return pageNum}public void detail(){System.out.println("书名："+this.title+"\n页数："+this.pageNum)}}
