Runtime

src/chapter5/Example11.java

@@ -1,5 +1,9 @@
 package chapter5;
 
+/**
+ * 获取当前时间
+ */
+
 public class Example11 {
     public static void main(String[] args) {
         long startTime = System.currentTimeMillis();

src/chapter5/Example12.java

@@ -0,0 +1,21 @@
+package chapter5;
+
+import java.util.Enumeration;
+import java.util.Properties;
+
+/**
+ * 获取系统信息
+ */
+public class Example12 {
+    public static void main(String[] args) {
+        // 获取当前系统信息
+        Properties prop = System.getProperties();
+        Enumeration names = prop.propertyNames();
+        while (names.hasMoreElements()) {
+            String key = (String) names.nextElement();
+            String value = prop.getProperty(key);
+            System.out.println(key + "=" + value);
+        }
+    }
+}
+

src/chapter5/Example13.java

@@ -0,0 +1,28 @@
+package chapter5;
+
+class Person implements AutoCloseable {
+    String name;
+    public Person(String name) {
+        this.name = name;
+    }
+
+    public void close() {
+        System.out.println( name + " 要被回收啦！");
+    }
+}
+
+public class Example13 {
+    public static void main(String[] args) {
+        Person p1 = new Person("小明");
+        Person p2 = new Person("大王");
+
+        p1 = null;
+        p2 = null;
+
+        System.gc();
+
+        for (int i = 0; i < 1000000; i ++) {
+            // 为了延长程序运行的时间
+        }
+    }
+}

src/chapter5/Example14.java

@@ -0,0 +1,15 @@
+package chapter5;
+
+/**
+ * 获取当前虚拟机信息
+ */
+
+public class Example14 {
+    public static void main(String[] args) {
+        Runtime rt = Runtime.getRuntime();
+        System.out.println("处理器个数：" + rt.availableProcessors());
+        System.out.println("空闲内存：" + rt.freeMemory()/1024/1024 + "MB");
+        System.out.println("虚拟机中的内存总量：" + rt.totalMemory()/1024/1024 + "MB");
+        System.out.println("最大可用内存：" + rt.maxMemory()/1024/1024 + "MB");
+    }
+}