Java程序设计第1-4章练习题参考答案(6)

} }

10、以下程序的输出结果为＿＿＿＿。 class Person {

private String name; public Person() { this(\陈敏\ }

public Person(String setName) { name = setName; }

public String getName() { return name; } }

class Teacher extends Person { private String id;

public Teacher(String s1, String s2) { super(s1);

id = s2; }

public String getId() { return id; } }

public class Test {

public static void main(String[] args) {

Teacher t = new Teacher(\黄牧\ System.out.println(t.getName()); System.out.println(t.getId()); } }

12、以下程序的输出结果为＿＿＿＿＿＿＿＿。 interface Runner {

public abstract void run(); }

class Dog

implements Runner {

public void run() {

System.out.println(\ } }

class Horse

implements Runner { public void run() {

System.out.println(\ } }

public class Test {

public static void run(Runner r) { r.run(); }

public static void main(String[] args) { Runner horse = new Dog(); run(horse); } }

13、编程判断指定的字符串是否是合法的Java标识符？请在空白处填上适当的语句。 public class Identifier {

public static boolean isIdentifier(String str) {

if (str!=null && str.length()>0) {

char ch = str.charAt(0); if ( ) {

for (int i=1; i

ch = str.charAt(i);

if (!(ch>='A' && ch<='Z' || ch>='a' && ch<='z' || ch=='_' || ch=='$' || ch>='0' && ch<='9'))

____________________________

}

_______________________________

} }

return false;

}

public static void main(String args[]) {

String str = \ if (args.length>0)

str=args[0];

System.out.println(\}

14、可计算面积的接口与实现该接口的矩形类

interface Area //定义可计算面积接口 {

_________________________________; //计算面积的抽象方法 }

public class Rectangle ________________________ //定义矩形类，实现接口Area {

protected double length, width; //长度和宽度

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