Arrays.asList,for hashmap

import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class StringFinal {

public static void main(String args[]){

String a = "ggggfffddd";

String b = a.replace('g', 't');
System.out.println(a);
System.out.println(b);

String strArr[] ={"A","B","C"};

List list = Arrays.asList(strArr);
list.set(1, "D");//list和strArr是引用 关系的，更改之后 strArr同步修改
//list.add("E");//这句抛出 java.lang.UnsupportedOperationException
for(int i=0;i<strArr.length;i++){
System.out.println(strArr[i]);
}

for(Iterator it = list.iterator();it.hasNext();){
String kd = (String) it.next();
}

//对于foreach，只能访问元素的内容，但是无法访问元素的索引
for(String x : strArr){
System.out.println(x);
}

Map map = new HashMap();

//Set set = map.entrySet();这里返回的是set，不能进行迭代

map.put("key1","value1");
map.put("key2","value2");
map.put("key3",null);
map.put(null,null);
//这里进行map的遍历
for(Iterator it = map.keySet().iterator();it.hasNext();){
String temp = (String)it.next();
System.out.println(temp+":"+map.get(temp));
}

Iterator it = map.entrySet().iterator();
while(it.hasNext()){
Map.Entry me = (Map.Entry)it.next();
System.out.println(me.getKey()+":"+me.getValue());
}

}
}