list map

demo1/src/test/java/cn/freemud/demo/HomeworkTests.java

+package cn.freemud.demo;
+
+import org.junit.Test;
+
+import java.util.*;
+
+public class HomeworkTests {
+
+    /**
+     * hashmap   set  arraylist linkedlist io
+     */
+
+    //arraylist:适合查询
+    //linkedlist：适合插入
+    @Test
+    public void alistDemp(){
+        List<Integer> array = new ArrayList<Integer>();
+        array.add(1);
+        array.add(2);
+        array.add(3);
+        for (Integer i:array){
+            System.out.println(i);
+        }
+    }
+
+
+    @Test
+    public void llistDemp(){
+        List<Integer> linklist = new LinkedList<>();
+        linklist.add(1);
+        linklist.add(2);
+        linklist.add(3);
+        for (Integer i:linklist){
+            System.out.println(i);
+        }
+    }
+
+
+    /**
+     * hashmap
+     */
+    @Test
+    public void hashmapDemo(){
+        Map map = new HashMap();
+        map.put("a","hello");
+        map.put("b"," world");
+        map.put("c","!");
+
+        Iterator iterator = map.keySet().iterator();
+        while (iterator.hasNext()){
+            Object key = iterator.next();
+            System.out.print(map.get(key));
+        }
+    }
+
+    @Test
+    public void setDemo(){
+        Set<Integer> setdemo = new TreeSet<>();
+        setdemo.add(1);
+        setdemo.add(2);
+        setdemo.add(3);
+        for (Integer a:setdemo)
+            System.out.print(a+" ");
+    }
+
+}