How can I simulate or write a code that would indicate that Java blocks a function till it has finished its execution. This way I will be able to show that Java has non-blocking I/O.

What I thought as my initial solution was to make an infinite loop but that didn't work as it will never finish its execution.

my other solution was to make a REST API and in that get request would delay and return something and think this might work but is there a native way to do it?

Here is the Java code below I want to delay the method fun2() without creating a new thread.

public class SetTimeOut {
     public static void  fun1(String str){
         System.out.println(str);
     }
    public static void fun2(String str){
       //how to make this function wait for 3 sec?
       System.out.println(str);  
    }
    public static void fun3(String str){
        System.out.println(str);
    }

    public static void main(String[] args) {
        fun1("Hello from fun1 is being called");
        fun2("Hello from fun2 is being called");
        fun3("Hello from fun3 is being called");
    }
}

Here is an equivalent JavaScript code to show that JavaScript has a non-blocking I/O. Want to simulate a similar kind of behavior in Java.

console.log("Hey");

setTimeout(() => {
   console.log("there!")
},3000);

console.log("please help");

just want to write something similar in java but it should block till the execution of the setTimeout() function is complete.

CodePudding user response：

tl;dr

You can pause execution of a thread.

Thread
.sleep( 
    Duration.ofSeconds ( 7 ) 
)

Sleep

As discussed in comments, you can sleep the thread for a specific length of time. The static method Thread.sleep method pauses execution of the current thread.

See Pausing Execution with Sleep in The Java Tutorials by Oracle Corp.

Thread.sleep( Duration.of… ( … ) ) ;

For example, sleep a half second.

Thread.sleep( Duration.ofMillis ( 500 ) ) ;  // A half-second.

Or seven seconds.

Thread.sleep( Duration.ofSeconds ( 7 ) ) ;  // Seven seconds.

Or half a day.

Thread.sleep( Duration.ofHours ( 12 ) ) ;  // Twelve hours.

Prior to Java 19

Before Java 19 , you must pass a mere int rather than a Duration, as a count of milliseconds.

For example, here we pause for a half-second.

Thread.sleep( 500 ) ;  // 500 milliseconds is a half-second. 

In Java 8 through Java 18, no need for you to do the math to get milliseconds. Use Duration#toMillis.

Thread.sleep( Duration.ofMinutes( 1 ).plusSeconds( 30 ).toMillis() ) ;  // 1.5 minutes as a count of milliseconds.