public class TestSeven extends Thread { private static int x; public synchronized void doThings() { int current = x; current++; x = current; } public void run() { doThings(); } } Which is true?()
第1题:
interface A{
int x = 0;
}
class B{
int x =1;
}
class C extends B implements A {
public void pX(){
System.out.println(x);
}
public static void main(String[] args) {
new C().pX();
}
}
错误。在编译时会发生错误(错误描述不同的JVM 有不同的信息,意思就是未明确的
x 调用,两个x 都匹配(就象在同时import java.util 和java.sql 两个包时直接声明Date 一样)。
对于父类的变量,可以用super.x 来明确,而接口的属性默认隐含为 public static final.所以可
以通过A.x 来明确。
第2题:
1.class TestSuper { 22.TestSuper(int i) { } 3. } 4.class TestSub extends TestSuper{ } 5.class TestAll { 6.public static void main (String [] args) { 7.new TestSub(); 8.} 9.} Which is true?()
第3题:
本题中,鼠标在窗口中单击一下,就在单击的位置生成一个小矩形,如果在小矩形上双击鼠标左键,则删除小矩形。 import java.awt.*; import java.awt.event.*; import javax swing.*; class MousePanel extends JPanel extends MouseMo- tionListener {public MousePanel {addMouseListener(new MouseAdapter {public void mousePressed(MouseEvent evt) {int X=evt.getX; int Y=evt.getY; current=find(x,y); if(current<0) add(x,y); } public void mouseClicked(MouseEvent evt) {int X=evt.getX; int Y=evt.getY; if(evt.getClickCount>=2) {remove(current); } } }); addMouseMotionListener(this); } public void paintComponent(Graphics g) {super.paintComponent; for(int i=0;i<nsquares;i++) draw(g,i); } public int find(int X,int y) (for(int i=0;i<nsquares;i++) if(squares[i].x-SQUARELENGTH/2<= x X<=squares[i].x+SQuARELENGTH/2 squares[i].Y-SQUARELENGTH/2< =Y y<=squares[i].Y+SQUARELENGTH /2) return i ; return-1 ; } public void draw(Graphics g,int i) {g.drawRect(squares[i].X-SQUARE- LENGTH/2。 squares[i].Y-SQUARELENGTH/2, SQUARELENGTH, SQUARELENGTH); } public void add(int X,int Y) {if(nsquares<MAXNSQUARES) {squares[nsquares]=new Point(x,y); current=nsquares ; nsquares++; repaint; } } public void remove(int n) {if(n<0 ‖ n>=nsquares)return; Nsquares- -; squares[n]=squares[nsquares]; if(current= =n)current= -l; repaint; } public void mouseMoved(MouseEvent evt) {} public void mouseDragged(MouseEvent evt) {} private static final int SQUARELENGTH=10: private static final int MAXNSQUARES=100; private Point[]squares=new Point[MAX- NSQUARES]; private int nsquares=0; private int current=-l; } class MouseFrame. extends JFramc {public MouseFrame {setTitle("java3"); setSize(300,200); addWindowListener(new WindowAdapter {public void windowClosing(WindowEvent e) {System.exit(0); } }); Container contentPane=getContentPane; contentPane.add(MousePanel); } } public class java3 {public static void main(String[]args) {JFrame. frame=new MouseFrame; frame.show; } }
第4题:
public class SyncTest ( private int x; private int y; private synchronized void setX (int i) (x=1;) private synchronized void setY (int i) (y=1;) public void setXY(int 1)(set X(i); setY(i);) public synchronized Boolean check() (return x !=y;) ) Under which conditions will check () return true when called from a different class?
第5题:
public class SyncTest { private int x; private int y; private synchronized void setX( int i ) { x = i; } private synchronized void setY( int i ) { y = i; } public void setXY( int i ) { setX(i); setY(i); } public synchronized boolean check() { return x != y; } } Under which condition will check return true when called from a different class? ()
第6题:
public class Threads5 { public static void main (String[] args) { new Thread(new Runnable() { public void run() { System.out.print(”bar”); } }).start(); } } What is the result?()
第7题:
Which are syntactically valid statement at// point x?() class Person { private int a; public int change(int m){ return m; } } public class Teacher extends Person { public int b; public static void main(String arg[]){ Person p = new Person(); Teacher t = new Teacher(); int i; // point x } }
第8题:
下列哪个方法可用于创建一个可运行的类? ( )
A.public class X implements Runable {public void run(){...,.,}}
B.public class X implements Thread {public void run(){......}}
C.public class X implements Thread {public int run(){……}}
D.public class X implements Runable {protected void run(){.....}}
第9题:
interface DeclareStuff{ public static final int EASY = 3; void doStuff(int t); } public class TestDeclare implements DeclareStuff { public static void main(String [] args) { int x=5; new TestDeclare().doStuff(++x); } void doStuff(int s) { s += EASY + ++s; System.out.println(”s “ + s); } } What is the result?()
第10题:
public class A extends Thread { A() { setDaemon(true); } public void run() { (new B()).start(); try { Thread.sleep(60000); } catch (InterruptedException x) {} System.out.println(“A done”); } class B extends Thread { public void run() { try { Thread.sleep(60000); } catch (InterruptedException x) {} System.out.println(“B done”); } } public static void main(String[] args) { (new A()).start(); } } What is the result?()