memorydemo.java

Java面向对象编程(随书配套源代码) 阐述了面向对象编程的思想

package chapter8;

class MemoryDemo
{
    public static void main(String args[])
    {
        Runtime r = Runtime.getRuntime();
        long mem1, mem2;
        Integer someints[] = new Integer[1000];
        System.out.println("Total mem is: " +
        r.totalMemory());
        mem1 = r.freeMemory();
        System.out.println("Initial free mem: " + mem1);
        r.gc();
        mem1 = r.freeMemory();
        System.out.println("Free mem after garbage collection: " + mem1);
        // 为Integer数组分配内存
        for(int i=0; i<1000; i++)
            someints[i] = new Integer(i);
        mem2 = r.freeMemory();
        System.out.println("Free mem after allocation: " + mem2);
        System.out.println("Mem used by allocation: " + (mem1-mem2));
        // 释放Integer数组所占用的内存
        for(int i=0; i<1000; i++) someints[i] = null;
            r.gc(); // 请求垃圾回收
        mem2 = r.freeMemory();
        System.out.println("Free mem after collecting discarded Ints: " + mem2);
    }
}