List<Object> list = new ArrayList<Object>(); list.add(xxx);for (int i = 0; i < list.size(); i++) { if (list.get(i) instanceof xxx) { //多少数据是list.size() //对象的话就instanceof } }
//总数量 int dataCount = listTest.size(); //指定类实例的数量 int objectCount = 0; for(int i=0;i<listTest.size();i++){ if(listTest.get(i) instanceof 指定雷鸣){ objectCount++; } }
封装?是保存数据吧? for example int recordCount = list.size(); int objCount = 0; for (int i=0; i<list.size(); i++) { Object obj = list.get(i); if (obj != 0 && obj.getClass() == SomeClass.class) { //如果子类也需要计算的话,用 obj instanceOf SomeClass objCount; } } System.out.printf("有%d条记录, 有%d个指定类对象\n", recordCount, objCount);
List看看有没有泛型的信息,如果有就很容易了,直接list.size()就可以看到List里面有多少数据 如果没有泛型信息,那么就得遍历list然后逐个计数了,利用instanceof判定import java.util.ArrayList; import java.util.List;/** * Created by IntelliJ IDEA. * User: Administrator * Date: 2011-9-22 * Time: 20:50:57 * To change this template use File | Settings | File Templates. */ public class ListDemo { public static void main(String[] args){ List list=new ArrayList(); list.add("abc"); list.add("cde"); list.add("fgh"); list.add(1); list.add(2); list.add(4); list.add(true); list.add(false); int stringNum=0; int booleanNum=0; int intNum=0; for(Object o:list){ if(o instanceof String){ stringNum++; } if(o instanceof Boolean){ booleanNum++; } if(o instanceof Integer){ intNum++; } } System.out.println("String元素数目"+stringNum); System.out.println("boolean元素数目"+booleanNum); System.out.println("int元素数目"+intNum); System.out.println("总共元素数目"+list.size()); } }
list.add(xxx);for (int i = 0; i < list.size(); i++) {
if (list.get(i) instanceof xxx) {
//多少数据是list.size()
//对象的话就instanceof
}
}
int dataCount = listTest.size();
//指定类实例的数量
int objectCount = 0;
for(int i=0;i<listTest.size();i++){
if(listTest.get(i) instanceof 指定雷鸣){
objectCount++;
}
}
for example
int recordCount = list.size();
int objCount = 0;
for (int i=0; i<list.size(); i++) {
Object obj = list.get(i);
if (obj != 0 && obj.getClass() == SomeClass.class) { //如果子类也需要计算的话,用 obj instanceOf SomeClass
objCount;
}
}
System.out.printf("有%d条记录, 有%d个指定类对象\n", recordCount, objCount);
如果没有泛型信息,那么就得遍历list然后逐个计数了,利用instanceof判定import java.util.ArrayList;
import java.util.List;/**
* Created by IntelliJ IDEA.
* User: Administrator
* Date: 2011-9-22
* Time: 20:50:57
* To change this template use File | Settings | File Templates.
*/
public class ListDemo { public static void main(String[] args){
List list=new ArrayList();
list.add("abc");
list.add("cde");
list.add("fgh");
list.add(1);
list.add(2);
list.add(4);
list.add(true);
list.add(false); int stringNum=0;
int booleanNum=0;
int intNum=0;
for(Object o:list){
if(o instanceof String){
stringNum++;
}
if(o instanceof Boolean){
booleanNum++;
}
if(o instanceof Integer){
intNum++;
}
}
System.out.println("String元素数目"+stringNum);
System.out.println("boolean元素数目"+booleanNum);
System.out.println("int元素数目"+intNum);
System.out.println("总共元素数目"+list.size());
}
}