Unit Data Structure.pptVIP

DataStruct 刘惠 029 座机电话号码 liuhui@sei.xidian.edu.cn Unit Objectives Describe the basic Java collection mechanisms Introduce the hierarchy of interfaces and classes for dealing with collections Data Structures A data structure can be thought of as a container that is used to group multiple elements into a single representation, and is used to store, retrieve, and manipulate the contained data Basic Data Structure Mechanisms Before the development of the Java2 platform, only a small set of classes and interfaces were available in the supplied Standard Class Library for data store manipulation. arrays Vector Stack Hashtable Properties BitSet Enumeration Vector addElement elementAt elements Vector 可以放不同类型的对象 必须存放对象引用，不能存放基本数据类型 根据下标操作 矢量数组的大小可以动态改变 常用API Stack 是Vector的子类 可以放不同类型的对象 只能放对象，而不能放基本数据类型 大小可以动态改变 采用后进先出原则 HashTable 从java.util.Dictionary抽象类继承而来 只能存放对象，不能存放基本数据类型 大小可以改变 可以放不同类型的对象 每一个对象必须与一个对象关键字对应 Array 两种定义形式： int[] a1; int a1[]; 数组初始化 int[] a1 1,2,3,4,5 ; 数组赋值 int[] a2; a2 a1; Java数组从元素0开始计数，最大元素编号是length-1 public class Arrays public static void main String[] args int[] a1 1, 2, 3, 4, 5 ; int[] a2; a2 a1; for int i 0; i a2.length; i++ a2[i]++; for int i 0; i a1.length; i++ prt a1[ + i + ] + a1[i] ; static void prt String s System.out.println s ; import java.util.*; public class ArrayClassObj public static void main String[] args Integer[] a new Integer[10]; prt length of a + a.length ; for int i 0; i a.length; i++ a[i] new Integer i ; prt a[ + i + ] + a[i] ; static void prt String s System.out.println s ; Properties 从java.util.Properties类继承而来 属性和属性值都是String类型 Maps keys to values Keys and values can be any non-null object Enumeration Interface The Enumeration interface allows the developer to traverse collections at a high level, with little concern for the underlying collection. Used specifically when traversal order is not important. Vectors elements method and Hashtables keys and elements met