public class RuntimeDemo {

     public static void main(String[] args) {

         Runtime runtime=Runtime.getRuntime();

         System.out.println("最大容量"+runtime.maxMemory()/1024/1024+"MBytes");

         System.out.println("CPUs : "+runtime.availableProcessors());

         System.out.println("Free Memory: "+runtime.freeMemory()/1024/1024+"MBytes");

         System.out.println("Total Memory:"+runtime.totalMemory()/1024/1024+"MBytes");

     }

 }

 import java.util.Enumeration;

 import java.util.Properties;

 public class SysInfo {

     public static void main(String[] args) {

         Properties properties=System.getProperties();//getProperties()用于获取当前系统的全部属性

         Enumeration<?> propertyNames=properties.propertyNames();

         while(propertyNames.hasMoreElements()) {

             String key=(String)propertyNames.nextElement();

             String value=System.getProperty(key);//System.getProperty()获得指定键描述的系统属性

             System.out.println(key+"---->"+value);

         }

 //        System.out.println("Java Version:"+System.getProperty("java.version"));

 //        System.out.println("OS Name:"+System.getProperty("os.name"));

 //        System.out.println("OS Version:"+System.getProperty("os.version"));

     }

 }

 import java.util.Arrays;

 public class ArrayCopy {

     public static void main(String[] args) {

         int[] data1 = {1, 2, 3, 4,5 };

         int[] data2 = new int[10];

         System.arraycopy(data1, 2, data2, 2, 3);

         System.out.println(Arrays.toString(data2));

     }

 }

 //结果显示：[0, 0, 3, 4, 5, 0, 0, 0, 0, 0]