JAVA程序执行内存分析.ppt

JAVA程序执行内存分析,内存分析,内存中的存放,code segment,data segment,stack,heap,存放代码,静态变量，字符串变量,局部变量,new出来的东西,Birthdate类,class BirthDate private int day; private int month; private int year; public BirthDate(int d,int m,int y) day=d;month=m;year=y; public void setDay(int d)day=d; public void setMonth(int m)month=m; public void setYear(int y)year=y; public int getDay()return day; public int getMonth()return month; public int getYear()return year; public void dispaly() System.out.println(day+“-“+month+“-“+year); ,Test类,public class Test public static void main(String args) Test test=new Test(); int date=9; BirthDate d1=new BirthDate(7,7,1970); BirthDate d2=new BirthDate(1,1,2000); test.change1(date); test.change2(d1); test.chang3(d2); System.out.println(“date=“+date); d1.display(); d2.display(); public void chang1(int i)i=1234; public void chang2(BirthDate b)b=new BirthDate(22,2,2004); public void chang3(BirthDate b)b.setDay(22); ,内存中变量存放说明,Test test=new Test(); test为局部变量，指向new出来的对象,test:xxx,stack,heap,内存中变量存放说明,int date; 定义局部变量，占一块内存,stack,date:9,内存中变量存放说明,BirthDate d1=new BirthDate(7,7,1970); 局部变量d1，指向new出来的对象,stack,d1:xxx,y1970,m7,d7,heap,day,month,year,构造方法调用结束后，d,m,y将被释放,内存中变量存放说明,test.change1(date); 调用Test中的change1方法,stack,date:9,i,i:9,i:1234,传值,赋值,调用结束，i被释放,内存中变量存放说明,test.change2(d1);,heap,stack,d1:xxx,b:xxx,day:7,month:7,year:1970,传地址,new:xxx,day:22,month:2,year:2004,传地址,1,2,3,4,5,6,方法调用结束后b和new消失,7,内存中变量存放说明,test.chang3(d2);,stack,heap,d2:xxx,b:xxx,day:1,month:1,year:2000,d:22,1,3,2,4,传值,传值,方法调用结束后b和d消失,5,三维坐标中的点,class Point int x,y,z; Point(int a,int b,int c) x=a;y=b;z=c; void getDistance(Point p) return (x-p.x)*(x-p.x)+(y-p.y)*(y-p.y)+(z-p.z)*(z-p.z); Point p1=new Point(1,2,3); System.out.println(“+getDistance(new Point(0,0,0);,上例内存分析,System.out.println(“+getDistance(new Point(0,0,0);,stack,heap,x:1,y:2,z:3,x:0,y:0,z:0,p1:xxx,p:xxx,1,3,2,传地址,调用结束后p被释放,this关键字的引用,public class Leaf int i=0; Leaf(int i)this.i=i; Leaf increament() i+;return this; void print()System.out.println(“i=“+i); public static void main(String args) Leaf leaf=new Leaf(100); leaf.increament().increament().print(); ,this关键字的引用,Leaf leaf=new Leaf(100);,stack,heap,this,i:100,i:100,调用结束后i被释放,leaf：xxx,想象this在类中,this关键字的引用,leaf.increament().increament().print();,leaf:xxx,this,i:102,leaf1:xxx,leaf2:xxx,this是当前对象的引用,stack,heap,this关键字的引用,leaf.increament().increament().print(); 相当于以下程序段： leaf.increament(); leaf.increament();leaf.print(); leaf.increament().increament().print();,返回leaf对象的引用l1，指向leaf对象,返回leaf对象的引用l2，指向leaf对象,内存分析（一）,class PointXY /分析程序在内存中执行过程 private double x; private double y; PointXY(double x1,double y1)x=x1;y=y1; public double getX()return x; public double getY()return y; public void setX(double i)x=i; public void setY(double i)y=i; ,内存分析（二）,class Circle private PointXY o; private double radius; Circle(PointXY p,double r)o=p;radius=r; Circle(double r) o=new PointXY(0.0,0.0);radius=r; boolean contains(PointXY p) double x=p.getX()-o.getX(); double y=p.getY()-o.getY(); if(x*x+y*yradius*radius) return false; else return true; public void setO(double x,double y) o.setX(x);o.setY(y); public PointXY getO()return o; public double getRadius()return radius; public void setRadius(double r)radius=r; public double area()return 3.14*radius*radius; ,内存分析（三）,public class TestCircle public static void main(String args) Circle c1=new Circle(new PointXY(1.0,2.0),2.0); Circle c2=new Circle(5.0); System.out.println(“c1:(“+c1.getO().getX()+“,“ +c1.getO().getY()+“),“+c1.getRadius(); System.out.println(“c2:(“+c2.getO().getX()+“,“+c2.getO().getY()+“),“+c1.getRadius(); System.out.println(“c1 area =“+c1.area(); System.out.println(“c2 area =“+c2.area(); c1.setO(5, 6);c2.setRadius(9.0); System.out.println(“c1=(“+c1.getO().getX()+“,“+c1.getO().getY()+“),“+c1.getRadius(); System.out.println(“c2=(“+c1.getO().getX()+“,“+c2.getO().getY()+“),“+c2.getRadius(); System.out.println(“c1 area =“+c1.area();System.out.println(“c2 area =“+c2.area(); PointXY p1=new PointXY(5.2,6.3); System.out.println(c1.contains(p1); System.out.println(c1.contains(new PointXY(10.0,9.0); ,Circle c1=new Circle(new PointXY(1.0,2.0),2.0);,c1:xxx,x:1.0,y:2.0,x1:1.0,y1:2.0,o,radius:2.0,p:xxx,r:2.0,紫色的调用结束后释放,红色的几位调用结束后内存布局,stack,heap,Circle c2=new Circle(5.0);,c2:xxx,o,radius:5.0,r:5.0,x1:0.0,y1:0.0,x:0.0,y:o.o,stack,heap,System.out.println(“c1:(“+c1.getO().getX()+“,“ +c1.getO().getY()+“),“+c1.getRadius();,c1:xxx,o,radius:2.0,x:1.0,y:2.0,和o里的值一样,1.0,返回值,返回值,stack,heap,2.0,返回值,c1.setO(5, 6);c2.setRadius(9.0);,o,radius:2.0,o,radius:5.09.0,x:1.05,y:2.06,x:0.0,y:0.0,c1:xxx,c2:xxx,x:5,y:6,i:5,i:6,r:9.0,heap,stack,System.out.println(c1.contains(p1);,o,radius:2.0,x:5,y:6,x:5.2,y:6.3,c1:xxx,p1:xxx,p:xxx,x,y,stack,heap,true,static关键字的使用,public class Cat private static int sid=0; private String name; int id; Cat(String name) =name; id=sid+; public void info System.out.println(“My name is “+name+“ NO.“+id); public static void main(String args) Cat.sid=100; Cat.mimi=new Cat(“mimi“); Cat.pipi=new Cat(“pipi“); (); (); ,static关键字的使用,stack,heap,data seg,sid:100101102,id:100,name,id:101,name,mimi:xxx,pipi:xxx,“mimi“,“pipi“,name,name,类的继承,student,Person,name,age,school,stack,heap,子类,父类,Java权限修饰符,super和this的使用,cc:xxx,valeu,value,this,super,子类,父类,Testsupr.class Stu s1=new Stu(“C“,“s1“);,pers,name,location,school,this,super,heap,“beijing“,“C“,“s1“,s1,name,school,n,l,school,name,location,data seg,stack,hashcodes table,hashcodes table,对象,对象,对象,对象,对象,每一个对象都有独一无二的hashcodes,通过它可以找到所在对象的位置,对象转型casting(TestAnimals),class Animal class Dg extends Animal Animal a=new Animal();/ a=new Dg();/ Dg d1=(Dg)a;/,对象转型casting(TestAnimals),Animal a,Animal,name,furcolor,程序中把a当成一只普通的Animal，不能访问Dg中的成员,Dg,不能访问,表明,实质,只能访问作为父类的那部分成员,Dg d1,动态绑定和多态(TestPolymoph),Cate c,name:catname,eyeColor:blue,name:“l1“,Anima pet,lady l1,实质上指向,code seg,Anima enjoy,Cate enjoy,Do enjoy,根据实际对象类型来调用,方法,星际的多态应用,父类GameObject,draw(),继承,使用多态,异常的概念,public void someMethod() throws SomeException if(someCondition() throw new SomeException(“错误原因“); ,声明该方法可能抛出的异常,构造并抛出异常对象,抛出异常,try someMethod(); catch(SomeException e) /异常处理代码； ,调用该方法时试图捕捉异常,定义处理异常的代码,异常的分类,Throwable,Error,Exception,RuntimeException,可抛出的,系统错误，处理不了,能处理的错误,经常出的错误，可以不catch,必须得catch的异常,运行时异常,非运行时异常,method() throws SomeException,包含,异常类的父类,异常的捕获和处理,try /可能抛出异常的语 catch(SomeException e1) catch(SomeException e2) finally,统一的出口，都要被执行，可进行资源的清除工作,readFile() throws IOException method1() throws IOException readFile() method2() throws IOException method1() public static main(String s) try method2() catch(IOException e) ,抛异常,抛异常,抛异常,捕获,处理,main方法可不处理，向外抛,int s; 数组定义 s=new int5;,xxx,s,stack,heap,自动初始化都为0,Date days; 数组分配空间和赋值 days=new Date3; for(int i=0;i3;i+) daysi=new Date(2004,4,i+1);,xxx,xxx,xxx,xxx,2004,4,1,2004,4,2,2004,4,3,days,stack,heap,数组动态初始化,int a;/定义 a=new int3;/分配空间 a0=1;a1=2;a2=3;/赋值 Date days;/定义 days=new Date2;/分配空间 days0=new Date(2004,4,1);/赋值 days1=new Date(2004,4,2);/赋值,数组定义与为数组元素分配空间和赋值分开进行,数组元素静态初始化,int a3=1,2,3; Date days= new Date(2004,4,1), new Date(2004,4,2), new Date(2004,4,3) ;,在定义数组的同时就分配空间和赋值,数组元素的默认初始化,数组是引用类型，它的元素相当于类的成员变量，因此数组分配空间后，每个元素也被按照成员变量的规则被隐式初始化,int a=new int3; System.out.println(a1); Date days=new Date3; System.out.prinyln(days2);,数组作为返回值,Date d,xxxx,返回值,数组模拟链表,1,2,3,4,0,5,0,1,5,4,3,2,3,4,5,0,2,0,2,3,4,5,删除该元素,二维数组,xxxx,a0,a2,a00,a01,a10,a11,a20,a21,heap,stack,a1,xxxx,xxxx,xxxx,a,一维数组,数组的数组,Java中多维数组的声明和初始化应按从高维到低维的顺序进行,int a=new int3; /动态初始化 a0=new int2; a1=new int4; a2=new int3; int a=new int35; /动态初始化 int a=4,2,13,32,424,32,1,32,12; /静态初始化 二维数组的访问：aij,二维数组的输出,int a=1,2,3,4,5,6,7,8,9; for(int i=0;ia.length;i+) for(int j=0;jai.length;j+) System.out.print (“a“+i+“+j+“=“+aij+“,“); System.out.println(); 该循环可用于二维数组的整体赋值和输出,二维字符串数组,数组元素,一维,字符串,二维,String类不可变,String s1=“hello“; String s2=“world“; s1+=s2;,“hello“,“world“,“helloworld“,s1,s2,新建的对象,不可变,不可变,容器API,Collection,Set,List,Map,HashSet,LinkedList,ArrayList,HashMap,无顺序，不可重复,有顺序，可重复(equals),一个一个向里装,一对一对向里装,Iterator容器,next,元素,游标,Array与Linked比较,去掉,Array,Linked,改时要建一个新的数组,读时沿着链表向下查找,InputStream流,PipedInputS