Tuesday, 3 October 2017

java - How do I break multiple foreach loops?





I have four foreach loops that iterate through the collections and based on a condition do something.



Here is the code that I am writing now:



boolean breakFlag = false;
String valueFromObj2 = null;
String valueFromObj4 = null;
for(Object1 object1: objects){
for(Object2 object2: object1){
// I get some value from object2

valueFromObj2 = object2.getSomeValue();
for(Object3 object3 : object2){
for(Object4 object4: object3){
// Finally I get some value from Object4.
valueFromObj4 = object4.getSomeValue();
// Compare with valueFromObj2 to decide either to break all the foreach loop
breakFlag = compareTwoVariable(valueFromObj2, valueFromObj4 );
if(breakFlag){break;}
} // fourth loop ends here
if(breakFlag){break;}

} // third loop ends here
if(breakFlag){break;}
} // second loop ends here
if(breakFlag){break;}
} // first loop ends here


The main object (objects in the code) comes from a third-party provider SDK, so I cannot change anything on that portion. I want to ask the Stack Overflow community if there is a better approach to break all the four foreach loops. Or if there is any other way to refactor this code to make it more readable and maintainable.


Answer



Use a label on the outermost loop, and include this label in the break statement when you want to jump out of all the loops. In the example below, I've modified your code to use the label OUTERMOST:




String valueFromObj2 = null;
String valueFromObj4 = null;
OUTERMOST: for(Object1 object1: objects){
for(Object2 object2: object1){
//I get some value from object2
valueFromObj2 = object2.getSomeValue();
for(Object3 object3 : object2){
for(Object4 object4: object3){
//Finally I get some value from Object4.

valueFromObj4 = object4.getSomeValue();
//Compare with valueFromObj2 to decide either to break all the foreach loop
if( compareTwoVariable(valueFromObj2, valueFromObj4 )) {
break OUTERMOST;
}
}//fourth loop ends here
}//third loop ends here
}//second loop ends here
}//first loop ends here


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