JAVA5的新特性收集

一、java5特性:增强FOR循环

遍历数组 
语法: 
--------new--------- 
for(Type value:array) { 
    expression value; 
} 
--------old--------- 
for(int i = 0;i < array.length; i++){ 
int n = arrar[i]; 
do something; 
} 

遍历集合 
注意：for-each循环遍历的集合必须是实现Iterable接口  
语法: 
--------new--------- 
for (Type value:Iterable) ...{ 
    expression value; 
} 
--------old--------- 
for(Iterator iter = list.iterator(); iter.HasNext();){ 
Object o = iter.next(); 
do something; 
} 

例子： 
遍历数组 
求一个数组中所有的值的和. 
----------------old----------------- 
void testArrayOld(){ 
   int[] arrayOld = {1,2,3,4}; 
   int totalOld = 0; 
   for(int i = 0;i < arrayOld.length;i++){ 
       totalOld += arrayOld[i]; 
   }    
   System.out.println(totalOld); 
} 

----------------new----------------- 
void testArrauNew(){ 
    int[] array = {1,2,3,4}; 
    int totalNew = 0; 
    int i = 0; 
    for(int n:array){ 
    //循环变量(i)不可见;n为循环变量 
    totalNew += n; 
    } 
    System.out.println(totalNew); 
} 


遍历集合 
拼接list中的所有字符。 
----------------old----------------- 
void testListOld(){ 
    List listOld = new ArrayList(); 
    listOld.add("Agile"); 
    listOld.add(" "); 
    listOld.add("Java"); 
    String strOld = ""; 
    for(Iterator iter = listOld.iterator();iter.hasNext();){ 
    String strTemp = (String)iter.next(); 
    strOld += strTemp; 
    } 
    System.out.println(strOld); 
} 

----------------new----------------- 
void testListNew(){ 
     List<String> listNew = new ArrayList<String>(); 
     listNew.add("Agile"); 
     listNew.add(" "); 
     listNew.add("Java"); 
    String str = ""; 
    for(String strTemp:listNew){ 
     str += strTemp; 
    } 
    System.out.println(str); 
} 

Java代码 

 import  java.util.ArrayList;
 import  java.util.Iterator;
 import  java.util.List;


 public   class  TestFor {
     public   static   void  main(String[] args) {
         //old 数组
         int [] arrayOld = { 1 , 2 , 3 , 4 };
         int  totalOld =  0 ;
         for ( int  i =  0 ;i < arrayOld.length;i++){
             totalOld += arrayOld[i];
         }
         System.out.println(totalOld);

         //new数组
         int [] array = { 1 , 2 , 3 , 4 };
         int  totalNew =  0 ;
         int  i =  0 ;
         for ( int  n:array){
             //循环变量(i)不可见;n为循环变量
             totalNew += n;
         }
         System.out.println(totalNew);

         //old list
         List listOld = new  ArrayList();
         listOld.add("Agile" );
         listOld.add(" " );
         listOld.add("Java" );
         String strOld = "" ;
         for (Iterator iter = listOld.iterator();iter.hasNext();){
             String strTemp = (String)iter.next();
             strOld += strTemp;
         }
         System.out.println(strOld);

         //new list
         List<String> listNew = new  ArrayList<String>();
         listNew.add("Agile" );
         listNew.add(" " );
         listNew.add("Java" );
         String str = "" ;
         for (String strTemp:listNew){
             str += strTemp;
         }
         System.out.println(str);
     }
 }