class A
{
public：
A．(){ doSth() }
virtual void doSth(){ printf("I am A");}
}
class B：public A
{
public：
virtual void doSth(){ printf("I am B");}
}
B． b;
执行结果是什么？为什么？
[单选题]请阅读下面程序 public class ThreadTest { public static void main(String args[]) throws Exception{ int i=0; Hello t=new Hello(); while(true) { System.out.println("Good Moming"+i++); if (i==2 && t.isAlive()) { System. out.println("Main waiting for
[单选题]请阅读下面程序 public class ThreadTest { public static void main(String args[]) throws Exception{ int i=0; Hello t=new Hello(); while(true) { System.out.println("Good Moming"+i++); if (i==2 && t.isAlive()) { System. out.println("Main waiting for
[主观题]请阅读下面程序public class Test {public static void main (String[] args) {int i，j;for (i=1；i＜5；i++) {for (j=1；j＜＝i;j++)system.out.print (i+"X"+j+"="+i*j+" ")；System.out.println()；}}}程序执行完后，i循环和j循环执行的次数分别是[ ]。
[单选题]请阅读下面程序 public class ThreadTest{ public static void main(String args[]) ( Thread t1=new Thread(new Hello()); Thread t2=new Thread(new Hello()); t1.start(); t2.start(); } } class Hello implements Runnable { int i; public void run() { while(true) { Sys
[单选题]请阅读下面程序 public class ThreadTest{ public static void main(String args[]) ( Thread t1=new Thread(new Hello()); Thread t2=new Thread(new Hello()); t1.start(); t2.start(); } } class Hello implements Runnable { int i; public void run() { while(true) { Sys
[单选题]请阅读下面程序 public class OperatorsAndExpressions { void residual() { int i=100, j=30; float m=563.5f, n=4.0f; System.out.println(i%j); System.out.println(m%n); } public static void main(String args[]) { OperatorsAndExpressions perAndExp=new OperatorsAndE
[单选题]请阅读下面程序 public class ExampleStringBuffer{ public static void main(String []args){ StringBuffer sb=new StringBuffer("test"); System.out.println("buffer="+sB) ; System.out.println("length="+sb.length());} } 程序运行结果中在"length="后输出的值A．10B．4C．20D．30
[单选题]请阅读下面程序 public class ExampleStringBuffer{ public static void main(String []args){ StringBuffer sb=new StringBuffer("test"); System.out.println("buffer="+sB) ; System.out.println("length="+sb.length());} } 程序运行结果中在"length="后输出的值A．10B．4C．20D．30
[试题]阅读下列程序段public class OperatorsAndExpressions {String conditionalExpression(int score) {String result;//如果score超过60分, 则结果是passed, 否则是doesn't passresult=-(score＞=60)?"passed":"doesn't pass";System.out.println(result);retum result;}public static voi
[单选题]阅读下面的程序段： public class Sun { public static void main(String args[ ]) { int a=0 for(int i=1;i＜=3;i++) { for(int j=1;j＜-i;j++) { for(int k=j;k＜=3;k++) { a=a+1; } } } System.out.println(A) 我; }}执行上面的3重循环后，a的值为( )。A．3B．9C．14D．21