java_Java快速入门练习.pdf
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1、 4 4.1 (1)(2)(3)(4)(5)JAVA 4.2 JAVA classobjectmethod 4 D-,;I-,;W-P-JAVA 4.3 Lab04,C:Lab04 Lab04 http:/javaLab/lab04.zip 4.4 .4.1:(D)4.4.1:(D)JAVA JAVA JAVA(class)(method)main applet paint JAVA JOptionPane showMessageDialog showInputDialog JOptionPane.showMessageDialog(null,Hi there!);String name=Jo
2、ptionPane.showInputDialog(Whats your name?);JOptionPane import 1.1 import javax.swing.JOptionPane;import JAVA javax.swing JOptionPane Integer parseInt String int Interger import java.lang IntegerJava Java Java Java ObjectClass 2.4-1Student.java/Student.java public class Student private int id;/ID pr
3、ivate String name;/public Student(int id,String name)this.id=id;this.name=name;public int getID()return id;public void setID(int id)this.id=id;public String getName()return name;public void setName(String name)this.name=name;Student 2 4 1 Student instance 3.JAVA JAVA Primitive Data TypeReference Dat
4、a Type Student s1,s2;/s1=new Student/Student 0 xabcdef s1 s2=s1/s1 s2 2 4.1:4.1 s1 s2 s1 s2 method Java constructorinstance methodstatic method(1)constructor Student Student s=new Student(123,he xiang);new s new Student s(2)instance method.()objectReference.methodName(parameters)Student s getID s.ge
5、tID();(3)static method JOptionPane showMessageDialog showInputDialog Integer parseInt.()ClassName.methodName(parameters)static methodstatic 4.3 (D)4.4.2:(D)Applet paint public void paint(Graphics g)()g Graphics()paint g Graphics paint Graphics drawString drawLine Font Font ft=new Font(Serif,Font.PLA
6、IN,56);g.setFont(ft);ft Font ft ft setFont Graphics g Java Graphics setFont public abstract void setFont(Font font)font setFont Font ft ftmain String()public static void main(String args)4.4.3(D)4.4.3:(D)1.Java local variableinstance variableclass variableparameter static Java JVM Java pseudocode cl
7、ass someClass visibility_modifier variable_type instanceVariableName;/Instance Variable visibility_modifier static variable_type classVariableName;/Class Variable returnType someMethod1()variable_type localVariableName;/Local Variable returnType someMethod2(Type parameterName)/Parameter instanceVari
8、ableName classVariableName someClass instanceVariableName classVariableName localVariableName someMethod parameterName someMehod2“”4 instanceVariableName,classVariableName,localVariableName parameterName(1)(2)“$”“_”(3)“$”“_”(4)myName MyName xvalue-1$amount 2brotherroom#class()2.Java VBJAVASCRIPT:typ
9、e identifier=value,identifier=value;int id;String name;3.4.Java 4.2 Java 4.2 5 catch if()int i=17;System.out.println(The value of i=+i);/if i if println if Java JVM ifwhile for if if Order orderDate Order orderDate orderDate JVM new JVM Order todayDate Order todayDate 5.6.VariableScope.java Java 4-2
10、VariableScope.java/VariableScope.java public class VariableScope/classVariableName static public String classVariableName=;/instanceVariableName private int instanceVariableName=0;/intParameter oneMethod public void oneMethod(int intParameter)/temp oneMethod 6 int temp=5;if(intParameter temp)/JAVA /
11、int temp=1;System.out.println(temp=+temp);instanceVariableName=instanceVariableName+intParameter;public void anotherMethod()System.out.println(+classVariableName);System.out.println(instanceVariableName=+instanceVariableName);public static void main(String args)/VariableScope /JVM VariableScope clas
12、sVariableName VariableScope object1=new VariableScope();/VariableScope System.out.println(+VariableScope.classVariableName);System.out.println(+object1.classVariableName);/object1 instancevariable1,instancevariable2 object1.oneMethod(6);object1.anotherMethod();/object1 instanceVariableName 4.4.4:(I)
13、(static)4.4.4:(I)1.Hello.java public class Hello public static void main(String args)System.out.println(Hello,world!);static main Java Hello static static-static “”“”static C 7 2.DrawX.java(4-3)ViewDrawX.html DrawX.java GraphicsUtility.java4-4 4-3DrawX.java/DrawX.java/Draws 3 big Xs./GraphicsUtility
14、 X.import java.applet.Applet;import java.awt.Graphics;import java.awt.Color;public class DrawX extends Applet public void paint(Graphics pen)setBackground(Color.black);pen.setColor(Color.white);GraphicsUtility.drawX(pen,0,0);GraphicsUtility.drawX(pen,4,0);GraphicsUtility.drawX(pen,29,35);/method pai
15、nt(Graphics)/class DrawX.java “X”DrawX.java GraphicsUtility.java DrawX.java drawLine GraphicsUtility drawX GraphicsUtility drawX X public static void drawX(Graphics g,int x,int y)g.drawLine(x,y,x+200,y+130);g.drawLine(x,y+130,x+200,y);/method drawX(Graphics,int,int)drawX public static void drawX(Gra
16、phics g,int x,int y)()4-4GraphicsUtility.java import java.awt.Graphics;public class GraphicsUtility public static void drawX(Graphics g,int x,int y)g.drawLine(x,y,x+200,y+130);g.drawLine(x,y+130,x+200,y);/method drawX /class GraphicsUtility 8 call DrawX paint GraphicsUtility drawX GraphicsUtility.dr
17、awX(pen,0,0);GraphicsUtility.drawX(pen,4,0);GraphicsUtility.drawX(pen,29,35);“X”drawX paint drawX Java Graphics g=pen;int x=0;int y=0;(formal parameter)actual parameterlocal variableGraphicsUtility application applet main “extends Applet”DrawX.java drawX“X”GraphicsUtility drawZ drawX “Z”“X”GraphicUt
18、ility.java drawZ drawX drawZ public static void drawZ(Graphics g,int x,int y)x y“Z”“Z”20 30 DrawXZ.java GraphicsUtility drawZ drawX Z X 201 110 applet HTML ViewDrawXZ.htmlz Z 0018009050X 3.4-5ViewDrawXZ.html applet X Z?drawZ drawZ GraphicsUtility 9 4.4.5(D)4.4.5:(D)1.MathUtility.java 4-6MathUtility.
19、java/MathUtility.java public class MathUtility public static double power(float base,int exponent)if(exponent 0)exponent=0-exponent;base=1/base;/if exponent 0 double product=1;for(int i=0;i exponent;i+)product*=base;return product;/method power(float,int)public static long power(int base,int exponen
20、t)if(exponent 0)System.err.println(:MathUtility.power(int,int)+exponent+0.);System.err.println(+);return 0;/if exponent 0 long product=1;for(int i=0;i exponent;i+)product*=base;return product;/method power(int,int)/class MathUtility power power float intpower int Java 2 2“method overload”10 MathUtil
21、ity.java power power double power long PowerTest1.java 4-7 2.4-7PowerTest1.java/PowerTest1.java/Tests the two power methods/in class MathUtility public class PowerTest1 public static void main(String args)final int intBase=2;final int exponent=50;final float floatBase=intBase;long longPower=MathUtil
22、ity.power(intBase,exponent);double doublePower=MathUtility.power(floatBase,exponent);System.out.println();/blank line System.out.println(intBase+exponent+:);System.out.println();System.out.println(+longPower+(long);System.out.println(+doublePower+(double unformatted);/method main /class PowerTest1 M
23、athUtility power 2 50 double double 1.125899906842624E15 1.125899906842624 10 15 float double 2 10 PowerTest1.java MathUtility power long longPower=MathUtility.power(intBase,exponent);double doublePower=MathUtility.power(floatBase,exponent);power longPower doublePower y=f(x)z=g(x,y)Java“”“”Pascal“”“
24、”C C+“11”MathUtility power return product;return power product 3.for(int i=0;i exponent;i+)product*=base;MathUtility power PowerTest2.java 4-8PowerTest2.java/PowerTest2.java/Tests the two power methods/in class MathUtility public class PowerTest2 public static void main(String args)final int intBase
25、=2;final int exponent=-3;final float floatBase=intBase;long longPower=MathUtility.power(intBase,exponent);double doublePower=MathUtility.power(floatBase,exponent);System.out.println();/blank line System.out.println(intBase+exponent+:);System.out.println();System.out.println(+longPower+(long);System.
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