2019.12.17 LeetCode 從零單刷個人筆記整理(持續更新)
github:https://github.com/ChopinXBP/LeetCode-Babel
Suppose we have a class:
public class Foo {
public void first() { print("first"); }
public void second() { print("second"); }
public void third() { print("third"); }
}
The same instance of Foo will be passed to three different threads. Thread A will call first(), thread B will call second(), and thread C will call third(). Design a mechanism and modify the program to ensure that second() is executed after first(), and third() is executed after second().
我們提供了一個類:
public class Foo {
public void one() { print(“one”); }
public void two() { print(“two”); }
public void three() { print(“three”); }
}
三個不同的線程將會共用一個 Foo 實例。
線程 A 將會調用 one() 方法
線程 B 將會調用 two() 方法
線程 C 將會調用 three() 方法
請設計修改程序,以確保 two() 方法在 one() 方法之後被執行,three() 方法在 two() 方法之後被執行。
示例 1:
輸入: [1,2,3]
輸出: "onetwothree"
解釋:
有三個線程會被異步啓動。
輸入 [1,2,3] 表示線程 A 將會調用 one() 方法,線程 B 將會調用 two() 方法,線程 C 將會調用 three() 方法。
正確的輸出是 "onetwothree"。
示例 2:
輸入: [1,3,2]
輸出: "onetwothree"
解釋:
輸入 [1,3,2] 表示線程 A 將會調用 one() 方法,線程 B 將會調用 three() 方法,線程 C 將會調用 two() 方法。
正確的輸出是 "onetwothree"。
注意:
儘管輸入中的數字似乎暗示了順序,但是我們並不保證線程在操作系統中的調度順序。
你看到的輸入格式主要是爲了確保測試的全面性。
package JUC;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
*
* Suppose we have a class:
* public class Foo {
* public void first() { print("first"); }
* public void second() { print("second"); }
* public void third() { print("third"); }
* }
* The same instance of Foo will be passed to three different threads. Thread A will call first(), thread B will call second(), and thread C will call third().
* Design a mechanism and modify the program to ensure that second() is executed after first(), and third() is executed after second().
* 我們提供了一個類:
* public class Foo {
* public void one() { print("one"); }
* public void two() { print("two"); }
* public void three() { print("three"); }
* }
* 三個不同的線程將會共用一個 Foo 實例。
* 線程 A 將會調用 one() 方法
* 線程 B 將會調用 two() 方法
* 線程 C 將會調用 three() 方法
* 請設計修改程序,以確保 two() 方法在 one() 方法之後被執行,three() 方法在 two() 方法之後被執行。
*
*/
class Foo {
private ReentrantLock lock;
private Condition condition1;
private Condition condition2;
private Condition condition3;
private volatile int idx;
public Foo() {
lock = new ReentrantLock();
condition1 = lock.newCondition();
condition2 = lock.newCondition();
condition3 = lock.newCondition();
idx = 1;
}
public void first(Runnable printFirst) throws InterruptedException {
lock.lock();
try{
while(idx != 1){
condition1.await();
}
// printFirst.run() outputs "first". Do not change or remove this line.
printFirst.run();
idx = 2;
condition2.signal();
}catch (Exception e){
e.printStackTrace();
}finally {
lock.unlock();
}
}
public void second(Runnable printSecond) throws InterruptedException {
lock.lock();
try{
while(idx != 2){
condition2.await();
}
// printSecond.run() outputs "second". Do not change or remove this line.
printSecond.run();
idx = 3;
condition3.signal();
}catch (Exception e){
e.printStackTrace();
}finally {
lock.unlock();
}
}
public void third(Runnable printThird) throws InterruptedException {
lock.lock();
try{
while(idx != 3){
condition3.await();
}
// printThird.run() outputs "third". Do not change or remove this line.
printThird.run();
}catch (Exception e){
e.printStackTrace();
}finally {
lock.unlock();
}
}
}
public class PrintInOrder {
}
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