Java determines whether a string is empty

The methods to determine whether a string str is empty are:

1. str!=null;

2. "".equals( str);

3. str.length()!=0;

Recommended: java video tutorial

Instructions:

1. Null means that this string does not point to anything. If you call its method at this time, a null pointer exception will occur.

2. "" means that it points to a string with a length of 0, and it is safe to call its method at this time.

3. null is not an object, "" is an object, so null does not allocate space, "" allocates space.

Example:

public void function1(String s,int n) {  
  long startTime = System.currentTimeMillis();  
   
  for(long i = 0; i<n; i++) {  
   if(s == null || s.equals(""));  
  }  
  long endTime = System.currentTimeMillis();  
   
  System.out.println("function 1 use time: "+ (endTime - startTime) +"ms");  
 }

public void function2(String str,int n) {  
  long startTime = System.currentTimeMillis();  
   
  for(long i = 0; i< n; i++) {  
   if(s == null || s.length() <= 0);  
  }  
  long endTime = System.currentTimeMillis();  
   
  System.out.println("function 2 use time: "+ (endTime - startTime) +"ms");  
 }

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