java.lang.IndexOutOfBoundsException in for each loop [duplicate]

Question

public String codeGeneration() { 

    ArrayList<String> dispatchTable = new ArrayList<String>();

    if(superEntry != null) { 
        ArrayList<String> superDispatchTable = getDispatchTable(superEntry.getOffset());

        for(int i = 0; i < superDispatchTable.size(); i++) {
            dispatchTable.add(i, superDispatchTable.get(i));
        }
    }

    String methodsCode = "";

    for(Node m : methods) {
        methodsCode+=m.codeGeneration();
        MethodNode mnode = (MethodNode) m;
        dispatchTable.add(mnode.getOffset(), mnode.getLabel());
    }
    addDispatchTable(dispatchTable);

    String codeDT = "";
    for(String s : dispatchTable) {
        codeDT+= "push " + s + "\n"
                + "lhp\n"
                + "sw\n" 
                + "lhp\n"
                + "push 1\n"
                + "add\n"
                + "shp\n"; 
    }

    return "lhp\n"
    + codeDT;
}

I get the following exception:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size: 0 at java.util.ArrayList.rangeCheckForAdd(Unknown Source) at java.util.ArrayList.add(Unknown Source)

The line which causes the error is: dispatchTable.add(mnode.getOffset(), mnode.getLabel());

Can anyone help me solve this? Thanks in advance.

If the List is empty you can't add an element at index 1. Use an array (you'll need to find the max offset first). Or a Map. — Elliott Frisch
– Elliott Frisch, Commented May 28, 2018 at 22:05
on that note, why are you using add(number, object) instead of just add(object)? — Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans, Commented May 28, 2018 at 22:28

Rostislav Krasny · Accepted Answer · 2018-05-28 22:56:59Z

-1

Quote from the javadoc of List#void add(int index, E element)

Throws:
...
IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())

In your case index == 1 and size() returns 0 because the dispatchTable list is still empty.

You better to change this:

ArrayList<String> dispatchTable = new ArrayList<String>();

if(superEntry != null) { 
    ArrayList<String> superDispatchTable = getDispatchTable(superEntry.getOffset());

    for(int i = 0; i < superDispatchTable.size(); i++) {
        dispatchTable.add(i, superDispatchTable.get(i));
    }
}

to this:

    List<String> superDispatchTable = superEntry != null ? getDispatchTable(superEntry.getOffset()) : Collections.EMPTY_LIST;
    List<String> dispatchTable = new ArrayList<>(superDispatchTable);

answered May 28, 2018 at 22:56

Rostislav Krasny

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