Merge remote-tracking branch 'origin/master'

XGerry · XGerry · commit be78a2bdde84 · 2018-12-12T22:52:33.000+08:00
# Conflicts:
#	src/ArrayListDemo.java
diff --git a/src/MapDemo.java b/src/MapDemo.java
@@ -1,13 +1,13 @@
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.Map;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 
 public class MapDemo {
     public static void main(String[] args) {
         Map<String, String> map = new HashMap<>();
         map.put("1", "Value1");
         map.put("2", "Value2");
         map.put("3", "Value3");
+        map.put(null, "11");
         //第一种：普遍使用，二次取值
         System.out.println("通过Map.keySet遍历key和value：");
         for (String key :
@@ -31,5 +31,12 @@ public static void main(String[] args) {
                 ) {
             System.out.println("key=" + entry.getKey() + " and value=" + entry.getValue());
         }
+        Vector vector = new Vector();
+        vector.add("11");
+
+//        Map<String,Integer> stringIntegerMap=new ConcurrentHashMap<>();
+//        stringIntegerMap.put(null,11);
+        HashSet hashSet = new HashSet();
+        hashSet.add(11);
     }
 }
diff --git a/src/StringDemo.java b/src/StringDemo.java
@@ -27,10 +27,27 @@ public static void main(String[] args) {
         System.out.println(stringBuffer);
         System.out.println(stringBuffer.reverse());
 
-        StringBuilder sb=new StringBuilder("Test1");
-        int size=sb.capacity();
+        StringBuilder sb = new StringBuilder("Test1");
+        int size = sb.capacity();
         System.out.println(size);
 
+        //System.exit(0);
+
+        String aa = new String("ab");
+        String bb = new String("ab");
+        String aaa = "ab";
+        String bbb = "ab";
+        System.out.println(aa.hashCode()+"/"+bb.hashCode()+"/"+aaa.hashCode()+"/"+bbb.hashCode());
+        if (aa == bb)
+            System.out.println("aa==bb");
+        if (aaa == bbb)
+            System.out.println("aaa==bbb");
+        if (aa.equals(bb))
+            System.out.println("aa equals bb");
+        if (aaa.equals(bbb))
+            System.out.println("aaa equals bbb");
+
+
     }
 }
 
