java常用容器用法实例(Hashtable,ArrayList,vector)
Hashtable 的用法package usehashtable; import java.util.Enumeration;import java.util.Hashtable; /**** @author Administrator*/public class UseHashtable { //创建Hashtable 对象 Hashtable ht=new Hashtable(); public UseHashtable() { } public void setHash(){ ht.put("1","a"); ht.put("2","b"); ht.put("3","c"); } public void getHash(){ //用key来标记hashtable中的索引 Enumeration key=ht.keys(); //allvalue标记hashtable中索引对应的值 Enumeration allvalue=ht.elements(); System.out.println("hashtable all keys:"); while(key.hasMoreElements()) { String str=(String)key.nextElement(); String strv=(String)allvalue.nextElement(); System.out.println(str+" : "+strv); } if(ht.containsKey("1")) System.out.println("has the value 1"); else System.out.println("do not contain 1"); ht.remove("1"); System.out.println("after remove the value 1:"); if(ht.containsKey("1")) System.out.println("has the value 1"); else System.out.println("do not contain 1"); if(ht.contains("c")) System.out.println("has the value c"); } public static void main(String[] args){ UseHashtable hs=new UseHashtable(); hs.setHash(); hs.getHash(); }}
Vector的用法
package usehashtable;import java.util.Vector;import java.util.Enumeration;/**** @author Administrator*/public class UseVector { Vector mainv=new Vector(); /** Creates a new instance of Vector */ public UseVector() { } public void setVector(){ //按照如下实例你可以存取数据库中一条记录里所有的字段值 Vector v1=new Vector(); v1.add("1"); v1.add("a"); v1.add("1a"); mainv.add(v1); Vector v2=new Vector(); v2.add("2"); v2.add("b"); v2.add("2b"); mainv.add(v2); Vector v3=new Vector(); v3.add("3"); v3.add("c"); v3.add("3c"); mainv.add(v3); } public void getVector(){ for(int i=0;i<3;i++) { for(int j=0;j<3;j++) { System.out.print(checkNull(i,j)+" "); } System.out.println(""); } } //只有值不为空时才返回他的值 public String checkNull(int row,int col) { try { if(!((String)((Vector)mainv.elementAt(row)).elementAt(col)).trim().equals(null)){ return ((String)((Vector)mainv.elementAt(row)).elementAt(col)); } else return ""; } catch(Exception e){ return ""; } } public static void main(String[] args){ UseVector uv=new UseVector(); uv.setVector(); uv.getVector(); }}
ArrayList的用法(借助一个Book类)
public class Book { private String bookName; private int bookPrice; /** Creates a new instance of Book */ public Book() { } public int getBookPrice() { return bookPrice; } public void setBookPrice(int bookPrice) { this.bookPrice = bookPrice; } public String getBookName() { return bookName; } public void setBookName(String bookName) { this.bookName = bookName; } } //ArrayList package usehashtable;import java.util.ArrayList;import java.util.Iterator;/**** @author Administrator*/public class UseArraylist { ArrayList ay=new ArrayList(); /** Creates a new instance of UseArraylist */ public UseArraylist() { } public void setArray(){ Book bk1=new Book(); bk1.setBookName("java"); bk1.setBookPrice(13); ay.add(0,bk1); Book bk2=new Book(); bk2.setBookName("jsp"); bk2.setBookPrice(30); ay.add(bk2); Book bk3=new Book(); bk3.setBookName("j2ee"); bk3.setBookPrice(20); ay.add(bk3); } public void getArray(){ Iterator i=ay.iterator(); while(i.hasNext()){ Book bk=(Book)i.next(); System.out.println(bk.getBookName()+" ,"+bk.getBookPrice()); } } public static void main(String[] args){ UseArraylist list=new UseArraylist(); list.setArray(); list.getArray(); }}
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