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);
    }
}