问答题
本题中定义了长度为20的一维整型数组a,并将数组元素的下标值赋给数组元素,最后打印输出数组中下标为奇数的元素。
public class java1(
public static void main(String[]args)
int a[]=______;
int i;
for(______;i++)
a[i]=i;
for(i=0;i<20;i++)
if(______)
System.out.print("a["+i+"]="+a[i]+",");
【参考答案】
第1处:new int[20]
第2处:i=0;i<20
第3处:i%2! =0
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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 MouseMotionListener 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); ); addMouseMorionListener(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-SQUARELENGTH 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=-1; 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[MAXNSQUARES]; private int nsquares=0; private int current=-1; class MouseFrame extends JFrame 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();
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问答题
本题中定义了一个树型的通信录,窗口左侧是一个树,右侧是一个文本域,单击树的结点,则在右侧文本域中显示相关信息,如果单击的是树结点,则显示对应名字的电话信息。 import javax.swing.*; import javax.swing.tree.*; import java.awt.*; import java.awt.event.*; import javax.swing.event.*; class Mytree2 extends JFrame JTree tree=null;JTextArea text=new JTextArea(20,20); Mytree2() Container con=getContentPane(); DefaultMutableTreeNode root=new DefauhMutableTreeNode( 同学通信录 ); DefaultMutableTreeNode t1=new DefauhMutableTreeNode( 大学同学 ); DefaultMutableTreeNode t2=new DefaultMutableTreeNode( 研究生同学 ); DefaultMutableTreeNode t1_1=new DefauhMutableTreeNode( 陈艳 ); DefaultMutableTreeNode t1_2=new DefauhMutableTreeNode( 李小永 ); DefaultMutableTreeNode t2_1=new DefauhMutableTreeNode( 王小小 ); DefaultMutableTreeNode t2_2=new DefauhMutableTreeNode( 董小 ); setTitle( java2 ); root.add(t1);root.add(t2); t1.add(t1_1);t1.add(t1_2);t2.add(t2_1);t2.add(t2_2); tree=new ITree(root); JScrollPane scrollpane=new JScrollPane(text); JSplitPane splitpane=new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, true,tree,scrollpane); tree.addTreeSelectionListener(this); con.add(splitpane); addWindowListener(Flew WindowAdapter() public void windowClosing(WindowEvent e) System.ext(0);))); setVisible(true);setBounds(70,80,200,300); public void valueChanged(TreeSelectionEvent e) if(e.getSource()==tree) DefaultMutableTreeNode node= (DefauhMutableTreeNode)tree.getLastSelectedPathComponent(); if(node.isLeaf()) String str=______; if(str.equals( 陈艳 )) text.setText(str+ :联系电话:0411-4209876 ); else if(str.equals( 李小永 )) text.setText(str+ :联系电话:010-62789876 ); else if(str.equals( 王小小 )) text.setText(str+ :联系电话:0430-63596677 ); else if(str.equals( 董小 )) text.setText(str+ :联系电话:020-85192789 );) else text.setText(node.getUserObject().toString()); public class java2 public static void main(String args[]) Mytree2 win=new Mytree2();win.pack();
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