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// FileName: SuperSub.java class superClass { int x;
superClass() { x=3;
System.out.println(“in superClass: x=”+x; )}
class subClass extends superClass {
int x; subClass() { super(); x=5;
System.out.println(“in subClass: x=”+x; )} class demo
{ public static void main(String args[]) {
subClass subc = new subClass(); }}
(6)
// FileName: Life.java import java.applet.Applet; import java.awt.* ;
class Life extends Applet {
public void showMessage(String newMessage)
{ System.out.println(newMessage); } public void init()
{ showMessage(\ public void start()
{ showMessage(\ public void stop()
{ showMessage(\ public void destroy()
{ showMessage(\
程序通过appletviewer运行，其中System.out.println语句输出的信息在控制台可查看。程序运行后在控制台看到的结果是什么？
(7)
public class Test { public static void main(String[] args) { Count myCount = new Count(); int times = 0; for(int i=0;i<100;i++)
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increment(myCount , times); System.out.println(“count is” + myCount.count); System.out.println(“time is”+ times); } public static void increment(Count c , int times) { c.count++; times++; } }
class Count { public int count; Count(int c) { count =c; } Count() { count =1;
} } 答案： count 101 times 0
(8)
public class Test { public static void main(String[] args) { Cirecle circle1 = new Circle(1); Cirecle circle2 = new Circle(2); // Attempt to swap circle 1 with circle2 System.out.println(“Before swap:circle1 = ”+circle1.radius +”circle2 = ”+circle2.radius); swap(circle1,circle2); System.out.println(“After swap: circle1 = ”+circle1.radius +”circle2 = ”+circle2.radius); } public static void swap(Circle x , Circle y) { System.out.println(“Before swap: x = ”+x.radius +”y = ”+y.radius); Circle temp = x; x = y; y = temp; System.out.println(“Before swap: x = ”+x.radius +”y = ”+y.radius); } }
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答案：
(9)
public class Foo { static int i=0; static int j=0; public static void main(String[] args) { int i=2; int k=3; { int j=3; System.out.println(“i + j is ”+ i + j); } k = i +j; System.out.println(“k is ”+k); System.out.println(“j is ”+ j); } } 答案： i + j is 23 k is 2 j is 0 (10)
class A
{ String s=\ void show() {
System.out.println(s); } } class B extends A
{ String s=\
void show() {
System.out.println(s); } } public class TypeConvert
{
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public static void main(String args[]) { B b1; B b2=new B();
A a1,a2; a1=(A)b2; a2=b2;
System.out.println(a1.s); a1.show(); System.out.println(a2.s); a2.show();
b1=(B)a1;
System.out.println(b1.s); b1.show(); System.out.println(b2.s);
b2.show();
}
}
答案: class A class B class A class B class B class B class B class B
17.下面是一个类的定义,根据题目要求回答以下问题.
class B { private int x;
private char y;
public B(int i,char j) { x=i; y=j;
}
public void show() { System.out.println(\
}
public void methodC(int x) {
this.x=this.x+x;
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y++; }
18.阅读程序，回答问题。
public class Test52 {
}
show();
String static str1=\ String static str2=\
public static void main(String args[])
{ System.out.print(str1); System.out.println(str2); } }
问题：1)这是哪种形式的 java 程序 ？（java应用程序） 2)程序的输出是什么？
（Hello, Java world! Hello, students! ）
19.阅读下面程序，回答问题： public class Foo { int i; static String s; void imethod() { } static void smethod() { } }
设f是Foo的一个实例，下列语句正确吗？ System.out.println(f.i); System.out.println(f.s); f.imethod(); f.smethod();
System.out.println(Foo.i); System.out.println(Foo.s); Foo.imethod(); Foo.smethod(); 答案： System.out.println(f.i);
答案： 正确
System.out.println(f.s);
答案： 正确 f.imethod();
答案： 正确
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