java: add «55. Jump Game»

URL:	https://leetcode.com/problems/jump-game/
Signed-off-by: Matej Focko <me@mfocko.xyz>

java/jump-game.java

@@ -0,0 +1,15 @@
+class Solution {
+  public boolean canJump(int[] nums) {
+    var last = 0;
+    for (var i = 0; i < nums.length && last < nums.length - 1; ++i) {
+      if (i > last) {
+        // can't reach the current position
+        return false;
+      }
+
+      last = Math.max(last, i + nums[i]);
+    }
+
+    return last >= nums.length - 1;
+  }
+}