/guava/guava/src/com/google/common/collect/Collections2.java
if ( nextPermutation == null) { nextPermutation = null; }
nextPermutation = null;
calculateNextPermutation(); return next; } void calculateNextPermutation() { int j = findNextJ(); if (j == -1) { <extra_id_0> return; } requireNonNull(nextPermutation); int l = findNextL(j); Collections.swap(nextPermutation, j, l); int n = nextPermutation.size();