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1,java String Integer等基本数据 引用不可改变原有值,除 原=New
2, List Map Set集合 引用可改变原有值
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class Test {
public static void main(String[] args) {
/**
* test String
*/
String s="str";
System.out.println(s);
testString(s);
System.out.println(s);
Integer i=1;
System.out.println(i);
testInteger(i);
System.out.println(i);
HashMap<String, String> hm=new HashMap<>();
hm.put("t", "a");
System.out.println(hm.toString());
testHashMap(hm);
System.out.println(hm.toString());
Set<String> hs=new HashSet<String>();
hs.add(s);
System.out.println(hs.toString());
testHashSet(hs);
System.out.println(hs.toString());
List<Object> l=new ArrayList<Object>();
l.add("1");
System.out.println(l.size());
testList(l);
System.out.println(l.size());
/**
* java String Integer等基本数据 引用不可改变原有值,除 原=New
* java List Map Set集合 引用可改变原有值
*/
}
public static void testString(String s){
s="new"+s;
}
public static void testHashMap(HashMap<String, String> hm){
hm.put("t", "b");
}
public static void testHashSet(Set<String> hs){
hs.add("new Set");
}
public static void testList(List<Object> l){
l.add("new");
}
public static void testInteger(Integer i){
i=i+1;
}
}