List的三種遍歷方式
阿新 • • 發佈:2019-01-11
package test1;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
List<Map<String,Object>> list = new ArrayList<Map<String, Object>>();
Map<String,Object> map1 = new HashMap<String, Object>();
List<String> list1 = new ArrayList<String>();
List<String> list2 = new ArrayList<String>();
List<String> list3 = new ArrayList<String>();
List<String> list4 = new ArrayList<String>();
list1.add("hello word 1");
list2.add("hello word 2");
list3.add("hello word 3");
list4.add("hello word 4");
map1.put("a",list1);
map1.put("b",list2);
list.add(map1);
Map<String,Object> map2 = new HashMap<String, Object>();
map2.put("c",list3);
map2.put("d",list4);
list.add(map2);
//第一種方式:
for (Map<String,Object> map:list) {
for (String s:map.keySet()) {
System.out.print("key:"+s+"\t");
System.out.println("value:"+map.get(s));
}
}
System.out.println("==========第一種方式結束===========");
//第二種方式:
for (int i = 0; i < list.size(); i++) {
Map<String, Object> map = list.get(i);
Iterator it = map.keySet().iterator();
while (it.hasNext()) {
String str = (String) it.next();
System.out.print("key:"+str+"\t");
System.out.println("value:"+map.get(str));
}
}
System.out.println("========第二種方式結束=============");
//第三種方式:
for (Map<String, Object> map : list) {
for (Map.Entry<String, Object> m : map.entrySet()) {
System.out.print("key:"+m.getKey() + " ");
System.out.println("value:"+m.getValue());
}
}
System.out.println("========第三種方式結束=============");
}
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
public class Test07 {
public static void main(String[] args) {List<Map<String,Object>> list = new ArrayList<Map<String, Object>>();
Map<String,Object> map1 = new HashMap<String, Object>();
List<String> list1 = new ArrayList<String>();
List<String> list2 = new ArrayList<String>();
List<String> list3 = new ArrayList<String>();
List<String> list4 = new ArrayList<String>();
list1.add("hello word 1");
list2.add("hello word 2");
list3.add("hello word 3");
list4.add("hello word 4");
map1.put("a",list1);
map1.put("b",list2);
list.add(map1);
Map<String,Object> map2 = new HashMap<String, Object>();
map2.put("c",list3);
map2.put("d",list4);
list.add(map2);
//第一種方式:
for (Map<String,Object> map:list) {
for (String s:map.keySet()) {
System.out.print("key:"+s+"\t");
System.out.println("value:"+map.get(s));
}
}
System.out.println("==========第一種方式結束===========");
//第二種方式:
for (int i = 0; i < list.size(); i++) {
Map<String, Object> map = list.get(i);
Iterator it = map.keySet().iterator();
while (it.hasNext()) {
String str = (String) it.next();
System.out.print("key:"+str+"\t");
System.out.println("value:"+map.get(str));
}
}
System.out.println("========第二種方式結束=============");
//第三種方式:
for (Map<String, Object> map : list) {
for (Map.Entry<String, Object> m : map.entrySet()) {
System.out.print("key:"+m.getKey() + " ");
System.out.println("value:"+m.getValue());
}
}
System.out.println("========第三種方式結束=============");
}
}
輸出結果:
key:bvalue:[hello word 2]
key:avalue:[hello word 1]
key:dvalue:[hello word 4]
key:cvalue:[hello word 3]
==========第一種方式結束===========
key:bvalue:[hello word 2]
key:avalue:[hello word 1]
key:dvalue:[hello word 4]
key:cvalue:[hello word 3]
==========第二種方式結束===========
key:b value:[hello word 2]
key:a value:[hello word 1]
key:d value:[hello word 4]
key:c value:[hello word 3]
==========第三種方式結束===========