簡單介紹使用java查看內存使用情況

使用java查看內存使用情況

public class test {
    public static <E> void main(String[] args) {
        Map<String, String> map = new HashMap<String, String>();
        final Runtime rt = Runtime.getRuntime();
        // jvm終止前記錄內存信息
        rt.addShutdownHook(new Thread() {
            public void run() {
                StringBuffer sb = new StringBuffer();
                long heapMaxSize = rt.maxMemory() >> 20;
                sb.append("最大可用內存" + heapMaxSize);
                long total = rt.totalMemory() >> 20;
                sb.append("堆內存大小:" + total);
                long free = rt.freeMemory() >> 20;
                sb.append("空閒內存大小:" + free);
                System.out.println(sb);
            }

        });
        // 放入400萬鍵值對
        for (int i = 0; i < 4000000; i++) {
            map.put("key" + i, "value" + i);
        }
    }
}