如何用Java中的线程解决死锁？

// Java program to illustrate Deadlock
// where deadlock occurs
// Importing required packages
import java.io.*;
import java.util.*;
// Class 1
// Helper class
class A {
    // Method 1 of this class
    // Synchronized method
    public synchronized void last()
    {
        // Print and display statement
        System.out.println("Inside A, last() method");
    }
    // Method 2 of this class
    // Synchronized method
    public synchronized void d1(B b)
    {
        System.out.println(
            "Thread1 start execution of d1() method");
        // Try block to check for exceptions
        try {
            // Putting the current thread to sleep for
            // specific time using slep() method
            Thread.sleep(2000);
        }
        // Catch block to handle the exceptions
        catch (InterruptedException e) {
            // Display the exception on the console
            System.out.println(e);
        }
        // Display statement
        System.out.println(
            "Thread trying to call B's last() method");
        // Calling the method 1 of this class as created
        // above
        b.last();
    }
}
// Class 2
// Helper class B
class B {
    // Method 1 of this class
    public synchronized void last()
    {
        // Display statement only
        System.out.println("Inside B, last() method");
    }
    // Method 2 of this class
    // Synchronized the method d2
    public synchronized void d2(A a)
    {
        // Display message only
        System.out.println(
            "Thread2 start execution of d2() method");
        // Try block to check for exceptions
        try {
            // Putting the current thread to sleep for
            // certain time using sleep() method
            Thread.sleep(2000);
            // Catch block to handle the exceptions
        }
        catch (InterruptedException e) {
            // Display the exception on the console
            System.out.println(e);
        }
        // Display message only
        System.out.println(
            "Thread2  trying to call A's last method");
        // Again calling the last() method inside this class
        a.last();
    }
}
// Class 3
// Main class
// Deadlock class which is extending Thread class
class GFG extends Thread {
    // Creating object of type class A
    A a = new A();
    // Creating object of type class B
    B b = new B();
    // Method 1
    public void m1()
    {
        // Starting the thread
        this.start();
        // Calling d1 method of class A
        a.d1(b);
    }
    // Method 2
    // run() method for the thread
    public void run()
    {
        // Calling d2 method of class B
        b.d2(a);
    }
    // Method 3
    // Main driver method
    public static void main(String[] args)
    {
        // Creating object of this class
        GFG deadlock = new GFG();
        // Calling m1 method
        deadlock.m1();
    }
}


// Java program to illustrate Deadlock
// where deadlock is pevented from occuring
// Importing required packages
import java.io.*;
import java.util.*;
// Class 1
// Helper class
class A {
    // Method 1 of this class
    // Synchronized method
    public synchronized void last()
    {
        // Print and display statement
        System.out.println("Inside A, last() method");
    }
    // Method 2 of this class
    // Synchronized method
    public synchronized void d1(B b)
    {
        System.out.println(
            "Thread1 start execution of d1() method");
        // Try block to check for exceptions
        try {
            // Putting the current thread to sleep for
            // specific time using slep() method
            Thread.sleep(2000);
        }
        // Catch block to handle the exceptions
        catch (InterruptedException e) {
            // Display the exception on the console
            System.out.println(e);
        }
        // Display statement
        System.out.println(
            "Thread trying to call B's last() method");
        // Calling the method 1 of this class as created
        // above
        b.last();
    }
}
// Class 2
// Helper class B
class B {
    // Method 1 of this class
    public void last()
    {
        // Display statement only
        System.out.println("Inside B, last() method");
    }
    // Method 2 of this class
    // Non-synchronized the method d2
    public void d2(A a)
    {
        // Display message only
        System.out.println(
            "Thread2 start execution of d2() method");
        // Try block to check for exceptions
        try {
            // Putting the current thread to sleep for
            // certain time using sleep() method
            Thread.sleep(2000);
            // Catch block to handle the exceptions
        }
        catch (InterruptedException e) {
            // Display the exception on the console
            System.out.println(e);
        }
        // Display message only
        System.out.println(
            "Thread2  trying to call A's last method");
        // Again calling the last() method inside this class
        a.last();
    }
}
// Class 3
// Main class
// Deadlock class which is extending Thread class
class GFG extends Thread {
    // Creating object of type class A
    A a = new A();
    // Creating object of type class B
    B b = new B();
    // Method 1
    public void m1()
    {
        // Starting the thread
        this.start();
        // Calling d1 method of class A
        a.d1(b);
    }
    // Method 2
    // run() method for the thread
    public void run()
    {
        // Calling d2 method of class B
        b.d2(a);
    }
    // Method 3
    // Main driver method
    public static void main(String[] args)
    {
        // Creating object of this class
        GFG deadlock = new GFG();
        // Calling m1 method
        deadlock.m1();
    }
}