java通過暴力反射創建不可實例化類的對象實例

以java.lang.Math爲例

Class b = Math.class; Constructor[]cc = b.getDeclaredConstructors(); Math t1=null,t2=null; for(int i =0;i<cc.length;i++) { cc[i].setAccessible(true); t1 = (Math)cc[i].newInstance(); t2 = (Math)cc[i].newInstance(); System.out.println(t1.abs(1)); System.out.println(t2.abs(1)); } System.out.println(t1 == t2);

 

要禁止此類情況，需要在jvm中加安全檢查參數-Djava.security.manager