Volatile(Object var1, long var2);
//将var4值放入指定var1对象的var2偏移量位置，直接刷新到主内存
public native void putLongVolatile(Object var1, long var2, long var4);
// 比较并替换原值为新值，操作成功返回true否则false，var1是指定对象，var2是偏移量地址，var4是预期的原值，var5是要更新的新值
public final native boolean compareAndSwapLong(Object var1, long var2, long var4, long var6);
// 自旋获取原值并增加数值，var1是指定对象，var2是偏移量地址，var4是要增加的值
public final int getAndAddLong(Object var1, long var2, long var4) {
int var5;
do {
var5 = this.getLongVolatile(var1, var2);
} while(!this.compareAndSwapLong(var1, var2, var5, var5 + var4));
return var5;
}
// 自旋获取原值并设置新值，var1是指定对象，var2是偏移量地址，var4是要设置的新值
public final int getAndSetLong(Object var1, long var2, long var4) {
int var5;
do {
var5 = this.getIntVolatile(var1, var2);
} while(!this.compareAndSwapLong(var1, var2, var5, var4));
return var5;
}
// 还有Object相关的cas操作这里没有列出
举几个栗子
public void test3() throws Exception {
Cat cat = new Cat("Kitty", 1000);
long speedOffset = unsafe.objectFieldOffset(Cat.class.getDeclaredField("speed"));
System.out.println("before putLongVolatile,getLongVolatile=" + unsafe.getLongVolatile(cat, speedOffset));
// 设置speed的值为2000
unsafe.putLongVolatile(cat, speedOffset, 2000);
System.out.println("after putLongVolatile,getLongVolatile=" + unsafe.getLongVolatile(cat, speedOffset));
// 到这里speed的值是2000，但是compareAndSwapLong里预期的值是3000，所以cas失败，返回false
System.out.println("compareAndSwapLong result:" + unsafe.compareAndSwapLong(cat, speedOffset, 3000, 4000));
// 到这里speed的值是2000，但是compareAndSwapLong里预期的值是2000，cas更新成功，返回true
System.out.println("compareAndSwapLong result:" + unsafe.compareAndSwapLong(cat, speedOffset, 2000, 4000));
// cas后speed的值就是4000了
System.out.println("after compareAndSwapLong,getLongVolatile=" + unsafe.getLongVolatile(cat, speedOffset));
// getAndAddLong会返回原值4000，新值=原值+10
System.out.println("getAndAddLong:" + unsafe.getAndAddLong(cat, speedOffset, 10));
// getAndAddLong后speed新值是4010
System.out.println("after getAndAddLong,getLongVolatile=" + unsafe.getLongVolatile(cat, speedOffset));
// getAndSetLong会返回原值4010，新值=要设置的新值1000
System.out.println("getAndSetLong:" + unsafe.getAndSetLong(cat, speedOffset, 1000));
// getAndSetLong后speed新值是1000
System.out.println("after getAndSetLong,getLongVolatile=" + unsafe.getLongVolatile(cat, speedOffset));
}
输出结果：
static...
before putLongVolatile,getLongVolatile=1000
after putLongVolatile,getLongVolatile=2000
compareAndSwapLong result:false
compareAndSwapLong result:true
after compareAndSwapLong,getLongVolatile=4000
getAndAddLong:4000
after getAndAddLong,getLongVolatile=4010
getAndSetLong:4010
after getAndSetLong,getLongVolatile=1000
线程调度及同步
// 释放线程让其继续执行，多次调用只会生效一次，可以在park前调用
public native void unpark(Object thread);
// 阻塞线程，isAbsolute为true：表示绝对时间，time的单位是毫秒ms，false：表示相对时间，time的单位是纳秒级的时间
public native void park(boolean isAbsolute, long time);
//以下3个方法均标注过期了，建议使用其他同步方法
// 获取var1的对象锁，没获取到则阻塞等待
public native void monitorEnter(Object var1);
// 尝试获取var1的对象锁，不阻塞，获取到则返回true，没获取到返回false
public native boolean tryMonitorEnter(Object var1);
// 释放var1对象锁
public native void monitorExit(Obje