在Java <= 0中是什么意思？0：1;

Question

I'm trying to understand this program in java but i'm new to this language.

Can you tell me what

<=0?0:1;

means?

It's from the following code that decrements the elements of a matrix (tabu)

 public void decrementTabu(){
        for(int i = 0; i<tabuList.length; i++){
           for(int j = 0; j<tabuList.length; j++){
            tabuList[i][j]-=tabuList[i][j]<=0?0:1;
         } 
        }
    }

Answer 1

You are not looking at the operator correctly.

This is the conditional operator ?: , which is the only ternary operator in JavaScript or Java (and other languages, such as C#). Ternary means it has three parameters.

Essentially this is what it means:

(condition)?(true branch):(false branch)
  param1        param2        param3

In your code example, the condition (param1) is:

tabuList[i][j]<=0

If true, 0 (param2) is returned. If false, 1 (param3) is returned.

The return value is then decremented from tabuList[i][j] via the -= operator.

The whole statement:

tabuList[i][j]-=tabuList[i][j]<=0?0:1;

Can be written as:

if (tabuList[i][j] > 0)
   tabuList[i][j]--;

Answer 2

tabuList[i][j]-=tabuList[i][j]<=0?0:1;

can be written as:

int tabuListEntry = tabuList[i][j];
tabuListEntry -=tabuListEntry <=0?0:1;

can be written as:

int tabuListEntry = tabuList[i][j];
tabuListEntry = tabuListEntry - (tabuListEntry <=0?0:1);

can be written as:

int tabuListEntry = tabuList[i][j];
int decrementAmount = tabuListEntry <=0?0:1;
tabuListEntry = tabuListEntry - decrementAmount ;

can be written as:

int tabuListEntry = tabuList[i][j];
int decrementAmount = 0; 
if(tabuListEntry  <= 0) {
    decrementAmount = 0;
} else {
    decrementAmount = 1;
}
tabuListEntry = tabuListEntry - decrementAmount ;

can be written as:

int tabuListEntry = tabuList[i][j];
int decrementAmount = 0; 
if(tabuListEntry  > 0) {
    decrementAmount = 1;
}
tabuListEntry = tabuListEntry - decrementAmount ;

can be written as:

int tabuListEntry = tabuList[i][j];
if(tabuListEntry  > 0) {
    tabuListEntry = tabuListEntry - 1;
}

Answer 3

This is work as if condition, will take "c<=0?0:1;"

This means if c is less than or equal to zero then answer is 0 else 1